schemachanger: deflate primary index chain logic include UWI constraint

[Xiang-Gu]

Previously, stmts like ADD COLUMN j INT, ADD UNIQUE WIHOUT INDEX (j) will fail with an internal error because we forget to process those unique-without-index in the DSC if the primary index chain has been inflated and needs to be deflated.

Fixes #118246
Release note (bug fix): Fix a bug where stmts like ADD COLUMN j INT, ADD UNIQUE WIHOUT INDEX (j) would fail with an internal error.

[cockroach-teamcity]

This change is 

[fqazi]

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

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pkg/sql/schemachanger/scbuild/internal/scbuildstmt/helpers.go line 1229 at r1 (raw file):

				e.IndexIDForValidation = new
			}
		case *scpb.UniqueWithoutIndexConstraint:

Should we add an end to end test with coverage of these scenarios? It could be a separate PR?

[Xiang-Gu]

I don't think we need a end-to-end test for this case -- IMO end-to-end tests are probably most useful when we support new DDLs in DSC and we need to see/understand more about the transitions. This particular case's transition is well charactered by existing add column, add check test, so, I think adding a logic test for this particular problematic stmt is enough.

bors r+

[craig]

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[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)