scbuild: fix concurrent schema change verification bug

[postamar]

Previously, we didn't check for concurrent schema changes on targets set
on elements that the builder state didn't know about yet. This patch
fixes this oversight. This regression was recently introduced by #106175.

Fixes: #106487

Release note: None

[cockroach-teamcity]

This change is 

[chengxiong-ruan]

nice

[postamar]

Thanks for the review. @rafiss has kindly agreed to run the tpce roachtest to validate this change, as I've been unable to do so on my gceworker (reprovisioning it would not be a good idea for other reasons)

[rafiss]

the roachtest is still in progress - in the meantime, i wanted to check if thought was given to trying to write a unit test that reproduces the bug. is there a reason that it would be too much of a challenge?

Reviewable status: complete! 0 of 0 LGTMs obtained

[rafiss]

still testing, but looks like my test made it past the part that is currently failing:

15:44:16 tpce.go:63: Installing docker
15:45:00 tpcc.go:1558: test status: setting up prometheus/grafana (<2m0s)
15:45:06 tpce.go:188: test status: initializing 5000 tpc-e customers
17:21:38 tpce.go:205: test status: running workload
17:21:38 cluster.go:2370: > sudo docker run cockroachdb/tpc-e:latest --customers 5000 --duration 2h0m0s --racks 3 --threads 12 --hosts=10.142.0.218 --hosts=10.142.0.221 --hosts=10.142.0.214

i still want us to think about a unit test for this, but if there's a significant barrier to adding one, i'm fine to merge this as is.

Reviewable status: complete! 0 of 0 LGTMs obtained

[postamar]

Thank you very much for the review and the testing! I'll file an issue re. test coverage.

bors r+

[postamar]

I filed #107223

[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 cd13eb4 to blathers/backport-release-22.2-106933: 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 22.2.x failed. See errors above.

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error creating merge commit from cd13eb4 to blathers/backport-release-23.1-106933: 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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