release-24.2: roachtest: various c2c/ldr improvements

[blathers-crl]

Backport 3/3 commits from #137275 on behalf of @msbutler.

/cc @cockroachdb/release

---

commit d422abf (HEAD -> butler-pcr-gcp-only, butler/butler-pcr-gcp-only)
Author: Michael Butler [email protected]
Date: Wed Dec 11 10:42:07 2024 -0500

roachtest: increase max accepted latency on c2c shutdown tests

The node shutdown tests occasionally fail when the latency exceeds 2 minutes;
however if the coordinator shutsdown, a new node may take up to two minutes to
adopt the job. This patch bumps the latency to 4 mintues to account for the job
system polling.

Informs #132730

Epic: none

commit cc2eb85
Author: Michael Butler [email protected]
Date: Wed Dec 11 10:38:26 2024 -0500

roachtest: only run ldr tests on gce

We cannot debug perf based failures on other clouds as we do not collect time
series metrics on them.

Epic: none

Release note: none

commit cd89447
Author: Michael Butler [email protected]
Date: Wed Dec 11 10:37:03 2024 -0500

roachtest: only run pcr tests on gce

We cannot debug perf based failures on other platforms without timeseries
metrics.

Epic: none

Release note: none

---

Release justification:

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
• Backports should not change on-disk formats or node communication protocols.
• Backports should not add new functionality (except as defined
  here).
• Backports must not add, edit, or otherwise modify cluster versions; or add version gates.
• All backports must be reviewed by the owning areas TL. For more information as to how that review should be conducted, please consult the backport
  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added).
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.
• Your backport must be accompanied by a post to the appropriate Slack
  channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[jeffswenson]

LGTM