sql: deflake TestTrackOnlyUserOpenTransactionsAndActiveStatements

[rafiss]

This changes the test to block in AfterExecute rather than OnTxnFinish, which should make the active statements assertion less flaky.

It also fixes a testing bug where the SELECT FOR UPDATE was not in a txn.

fixes #120042
fixes #120235
fixes #119829

Release note: None

[cockroach-teamcity]

This change is 

[fqazi]

Reviewed 5 of 5 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @abarganier, @msbutler, and @rafiss)

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pkg/sql/conn_executor_test.go line 1669 at r1 (raw file):

	params := base.TestServerArgs{}
	params.Knobs.SQLExecutor = &sql.ExecutorTestingKnobs{
		AfterExecute: func(ctx context.Context, stmt string, isInternal bool, err error) {

I'm guessing this was because OnRecordTxnFinish

[rafiss]

tftr!

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)
• macos_amd64_build
• macos_arm64_build
• windows_build

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from d6fd42f to blathers/backport-release-23.1-120505: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.1.x failed. See errors above.

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