opt/memo: fix optimizer_use_virtual_computed_column_stats

[michae2]

With optimizer_use_virtual_computed_column_stats set to false, constrained scans were still sometimes using stats on virtual computed columns. This commit adds a check to makeTableStatistics which prevents creation of any statistics referencing a virtual computed column, which is a stronger check than existed before.

With this check, the VirtualCols sets will always be empty when optimizer_use_virtual_computed_column_stats is false.

Informs: #68254

Epic: CRDB-8949

Release note: None

[cockroach-teamcity]

This change is 

[DrewKimball]

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

[michae2]

TFTR!

bors r=DrewKimball

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)
• check_generated_code
• docker_image_amd64
• examples_orms
• linux_amd64_build
• linux_amd64_fips_build
• linux_arm64_build
• 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.

---

error creating merge commit from 579d42e to blathers/backport-release-23.1-121171: 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.

---

error creating merge commit from 579d42e to blathers/backport-release-23.2-121171: 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 23.2.x failed. See errors above.

---

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}