This commit is a follow up to cockroachdb#45992. It adds some tests that were missed and
refactors the setup to a helper.

Fixes cockroachdb#45970.

```
--- PASS: TestPrimaryKeyChangeWithPrecedingIndexCreation (1.04s)
--- PASS: TestCRUDWhileColumnBackfill (0.73s)
--- PASS: TestIndexBackfillAfterGC (0.74s)
--- PASS: TestSchemaChangeGRPCError (0.67s)
--- PASS: TestFKReferencesAddedOnlyOnceOnRetry (0.50s)
```

Release justification: non-production code changes

Release note: None

46047: ui: Fix OOM exception while building Karma tests r=dhartunian a=koorosh

This exception was fixed in past and that
time main root cause was tied to Helmet library.

Now this OOM exception more likely is caused by
increasing code base.
Previously, webpack configuration provided to Karma
contained `devtool = sourcemap` and might caused
growing memory usage along with increased codebase.

To mitigate this problem as a quick fix during
stabilization period, following non-production
changes were made:
- Changed source maps generation for karma tests
to use lightweight 'eval' option
- `Sourcemap` preprocessors are removed

While testing locally, I couldn't get OOM exception
with following configs.

Related issue in Karma repo: karma-runner/karma#1868 (comment)

Release justification: Non-production code change

Release note: None

46132: sql: trace execution stats for query diagnostics r=RaduBerinde a=RaduBerinde

The distsql processors are initialized with the Context in the eval context. If
this context contains a tracing span that is recording, the processors will set
up statistics collection and put them in the span as tags.

The statement diagnostics code sets up a span but doesn't change this context,
so statistics collection doesn't happen. We want these statistics in the trace,
as they will soon be used to generate EXPLAIN ANALYZE diagrams for the bundles.

This change fixes this issue and moves up the initialization of the planner so
we can tweak it directly, which simplifies code.

Release note (bug fix): statement diagnostics traces now contain processor
statistics.

Release justification: Bug fixes and low-risk updates to new functionality

46179: sql: decrease job adopt interval for more schema change tests r=lucy-zhang a=ajwerner

This commit is a follow up to #45992. It adds some tests that were missed and
refactors the setup to a helper.

Fixes #45970.

```
--- PASS: TestPrimaryKeyChangeWithPrecedingIndexCreation (1.04s)
--- PASS: TestCRUDWhileColumnBackfill (0.73s)
--- PASS: TestIndexBackfillAfterGC (0.74s)
--- PASS: TestSchemaChangeGRPCError (0.67s)
--- PASS: TestFKReferencesAddedOnlyOnceOnRetry (0.50s)
```

Release justification: non-production code changes

Release note: None

Co-authored-by: Andrii Vorobiov <and.vorobiov@gmail.com>
Co-authored-by: Radu Berinde <radu@cockroachlabs.com>
Co-authored-by: Andrew Werner <ajwerner@cockroachlabs.com>