upgrades: add weaker column schema exists funcs for use with migrations

[andyyang890]

This patch adds two schema exists functions for use with migrations
that involve multiple schema changes on the same column(s) in order
to preserve the idempotence of the migration(s). They are weaker
in the sense that they do not check that the stored and final
expected descriptor match.

Informs #91449

Release note: None

[cockroach-teamcity]

This change is 

[ajwerner]

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @andyyang890 and @rafiss)

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pkg/upgrade/upgrades/schema_changes.go line 245 at r1 (raw file):

	storedTable, expectedTable catalog.TableDescriptor, colName string,
) (bool, error) {
	_, err := storedTable.FindColumnWithName(tree.Name(colName))

This lead to my filing #91924, but don't do anything about it here

[rafiss]

nice!

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @andyyang890)

[andyyang890]

TFTRs!

bors r=ajwerner,rafiss

[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 61cc346 to blathers/backport-release-22.2-91755: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 403 Resource not accessible by integration []

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

Backport to branch 22.2.x failed. See errors above.

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