32704: workload/ycsb: add flag to use column families r=nvanbenschoten a=nvanbenschoten

This change adds a new `--families` flag to the ycsb workload. Now
that #18168 is addressed, this significantly reduces the contention
present in the workload by avoiding conflicts on updates to different
columns in the same table.

I just confirmed that this still provides a huge speedup. On a 24 cpu machine:
```
workload run ycsb --init --workload='A' --concurrency=128 --duration=1m


--families=false gives:

_elapsed___errors_____ops(total)___ops/sec(cum)__avg(ms)__p50(ms)__p95(ms)__p99(ms)_pMax(ms)__total
   60.0s        0         103089         1718.0     13.9      0.6      1.8    604.0   1476.4  read
   60.0s        0         102947         1715.6     59.5      5.2     11.5   2281.7   8321.5  update

_elapsed___errors_____ops(total)___ops/sec(cum)__avg(ms)__p50(ms)__p95(ms)__p99(ms)_pMax(ms)__result
   60.0s        0         206036         3433.6     36.7      3.3      8.9   1342.2   8321.5


--families=true gives:

_elapsed___errors_____ops(total)___ops/sec(cum)__avg(ms)__p50(ms)__p95(ms)__p99(ms)_pMax(ms)__total
   60.0s        0         333477         5557.8      9.2      0.6      6.0    302.0   1275.1  read
   60.0s        0         332366         5539.3     13.7      6.8     17.8     54.5   4831.8  update

_elapsed___errors_____ops(total)___ops/sec(cum)__avg(ms)__p50(ms)__p95(ms)__p99(ms)_pMax(ms)__result
   60.0s        0         665843        11097.1     11.5      3.9     16.3    268.4   4831.8
```

cc. @robert-s-lee @drewdeally 

Release note: None

Co-authored-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>

This change marks all columns in the YCSB "usertable" as NOT NULL. Doing
so allows the load generator to take advantage of cockroachdb#44239, which avoids
the KV lookup on the primary column family entirely when querying one of
the other column families. The query plans before and after demonstrate
this:

```
--- Before
root@:26257/ycsb> EXPLAIN SELECT field5 FROM usertable WHERE ycsb_key = 'key';
    tree    |    field    |               description
------------+-------------+------------------------------------------
            | distributed | false
            | vectorized  | false
  render    |             |
   └── scan |             |
            | table       | usertable@primary
            | spans       | /"key"/0-/"key"/1 /"key"/6/1-/"key"/6/2
            | parallel    |

--- After
root@:26257/ycsb> EXPLAIN SELECT field5 FROM usertable WHERE ycsb_key = 'key';
    tree    |    field    |      description
------------+-------------+------------------------
            | distributed | false
            | vectorized  | false
  render    |             |
   └── scan |             |
            | table       | usertable@primary
            | spans       | /"key"/6/1-/"key"/6/2
```

This becomes very important when running YCSB with a column family per
field and with implicit SELECT FOR UPDATE (see cockroachdb#45159). Now that (as
of cockroachdb#45701) UPDATE statements acquire upgrade locks during their initial row
fetch, we don't want them acquiring upgrade locks on the primary column
family of the row they are intending to update a single column in. This
re-introduces the contention between writes to different columns in the
same row that column families helped avoid (see cockroachdb#32704). By marking each
column as NOT NULL, we can continue to avoid this contention.

This change marks all columns in the YCSB "usertable" as NOT NULL. Doing
so allows the load generator to take advantage of cockroachdb#44239, which avoids
the KV lookup on the primary column family entirely when querying one of
the other column families. The query plans before and after demonstrate
this:

```
--- Before
root@:26257/ycsb> EXPLAIN SELECT field5 FROM usertable WHERE ycsb_key = 'key';
    tree    |    field    |               description
------------+-------------+------------------------------------------
            | distributed | false
            | vectorized  | false
  render    |             |
   └── scan |             |
            | table       | usertable@primary
            | spans       | /"key"/0-/"key"/1 /"key"/6/1-/"key"/6/2
            | parallel    |

--- After
root@:26257/ycsb> EXPLAIN SELECT field5 FROM usertable WHERE ycsb_key = 'key';
    tree    |    field    |      description
------------+-------------+------------------------
            | distributed | false
            | vectorized  | false
  render    |             |
   └── scan |             |
            | table       | usertable@primary
            | spans       | /"key"/6/1-/"key"/6/2
```

This becomes very important when running YCSB with a column family per
field and with implicit SELECT FOR UPDATE (see cockroachdb#45159). Now that (as
of cockroachdb#45701) UPDATE statements acquire upgrade locks during their initial row
fetch, we don't want them acquiring upgrade locks on the primary column
family of the row they are intending to update a single column in. This
re-introduces the contention between writes to different columns in the
same row that column families helped avoid (see cockroachdb#32704). By marking each
column as NOT NULL, we can continue to avoid this contention.

This change marks all columns in the YCSB "usertable" as NOT NULL. Doing
so allows the load generator to take advantage of cockroachdb#44239, which avoids
the KV lookup on the primary column family entirely when querying one of
the other column families. The query plans before and after demonstrate
this:

```
--- Before
root@:26257/ycsb> EXPLAIN SELECT field5 FROM usertable WHERE ycsb_key = 'key';
    tree    |    field    |               description
------------+-------------+------------------------------------------
            | distributed | false
            | vectorized  | false
  render    |             |
   └── scan |             |
            | table       | usertable@primary
            | spans       | /"key"/0-/"key"/1 /"key"/6/1-/"key"/6/2
            | parallel    |

--- After
root@:26257/ycsb> EXPLAIN SELECT field5 FROM usertable WHERE ycsb_key = 'key';
    tree    |    field    |      description
------------+-------------+------------------------
            | distributed | false
            | vectorized  | false
  render    |             |
   └── scan |             |
            | table       | usertable@primary
            | spans       | /"key"/6/1-/"key"/6/2
```

This becomes very important when running YCSB with a column family per
field and with implicit SELECT FOR UPDATE (see cockroachdb#45159). Now that (as
of cockroachdb#45701) UPDATE statements acquire upgrade locks during their initial row
fetch, we don't want them acquiring upgrade locks on the primary column
family of the row they are intending to update a single column in. This
re-introduces the contention between writes to different columns in the
same row that column families helped avoid (see cockroachdb#32704). By marking each
column as NOT NULL, we can continue to avoid this contention.