Builtins defined using the UDF `Body` field will be wrapped in a `CASE`
expression if they are strict, i.e., `CalledOnNullInput=false`. When the
builtin is inlined, the `CASE` expression prevents decorrelation,
leaving a slow apply-join in the query plan. This caused a significant
regression of some ORM introspection queries.

Some of these builtins have filters that cause the SQL body to return no rows
if any of the arguments is NULL. In this case, the builtin will have the same
behavior whether or not it is defined as being strict. We can safely optimize
these builtins by setting `CalledOnNullInput=true`.

The following conditions are sufficient to prove that `CalledOnNullInput` can
be set for a builtin function with a SQL body:

  1. The WHERE clause of the SQL query *null-rejects* every argument of the
     builtin. Operators like `=` and `<` *null-reject* their operands because
     they filter rows for which an operand is NULL.

  2. The arguments are not used elsewhere in the query. This is not strictly
     necessary, but simplifies the proof because it ensures NULL arguments will
     not cause the builtin to error.

Examples of SQL statements that would allow `CalledOnNullInput` to be set:
```
SELECT * FROM tab WHERE $1=1 AND $2='two';

SELECT * FROM tab WHERE $1 > 0;
```

Fixes cockroachdb#96218
Fixes cockroachdb#95569

Epic: None

Release note: None