kill linux-build-lib from extended tests

[blaginin]

I don't think we need that anymore:

• the other extended tests are fast
• it makes some tests to wait for the check (4 mins bottleneck for the CI time)
• we have this base test in the main CI

[kosiew]

@blaginin
Thanks for the cleanup here. Approving with one small follow-up suggestion.

After this lands, it would be good to watch the first green run and confirm we get the CI latency improvement we want, and also make sure the removed pre-check job was not masking any early compile failures.

[kosiew]

Removing linux-build-lib seems like a good tradeoff to help unblock the long-running extended suite sooner.

Since the deleted job was still carrying the same ad hoc Rust/protobuf bootstrap that linux-test-extended keeps below, could we do a follow-up and move that setup into ./.github/actions/setup-builder or another shared helper?

I think that would make future CI environment changes a little easier to manage in one place.

[alamb]

Do we still want to merge this PR? It has been hanging out for a while

[blaginin]

We do! Missed the approval, thanks!

[alamb]

(I think it needs a merge up fro main to resolve conflicts and get all CI checks)