opt: prevent null-rejection rule cycle

[DrewKimball]

This patch adds checks to the null-rejection logic to ensure that null-rejection is not attempted when the necessary filter push-down rules are disabled. This prevents rule cycles that occur when decorrelation or filter elimination rules fire after the col IS NOT NULL filter isn't pushed all the way down to the outer join.

Fixes #89986

Release note: None

[cockroach-teamcity]

This change is 

[rytaft]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @DrewKimball)

[DrewKimball]

TFTR!

[DrewKimball]

bors r+

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[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 caa50f5 to blathers/backport-release-22.1-91561: 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 22.1.x failed. See errors above.

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[DrewKimball]

The machinery for preventing null-rejection when corresponding rules are disabled doesn't exist in 22.1.