Resume validator tests by using bazel 5

[antiphoton]

Fix #38610

[antiphoton]

@estherkim
The percy/amphtml test is flaky and failing. Please review the visual diff. I don't have the permission the review it in percy.io.

[estherkim]

@estherkim The percy/amphtml test is flaky and failing. Please review the visual diff. I don't have the permission the review it in percy.io.

Done!

[ampprojectbot]

Warning: disparity between this PR Percy build and its main build

The Percy build for this PR was approved (either manually by a member of the AMP team, or automatically if there were no visual diffs). However, during a continuous integration step we generated another Percy build using the commit on the main branch that this PR was merged into, and there appears to be a mismatch between the two.

This is possibly an indication of an issue with this pull request, but could also be the result of flakiness. Please inspect the two builds < This PR's Percy build / main commit's Percy build > and determine further action:

• If the disparity appears to be caused by this PR, please create an bug report or send out a new PR to fix
• If the disparity appears to be a flake, please @-mention ampproject/wg-approvers in a comment
• If there is no disparity and this comment was created by mistake, please @-mention ampproject/wg-infra
• If unsure, @-mention ampproject/wg-approvers

[estherkim]

Hi @antiphoton - looks like validator tests fail on main. Is Bazel installed correctly?

https://app.circleci.com/pipelines/github/ampproject/amphtml/26972/workflows/b06e6a83-8de3-43f4-bd83-e83dd6153bfc/jobs/564933

[estherkim]

another ping @antiphoton, @amaltas - a failure on main is blocking nightly cuts, which will prevent a new beta for next week's release cycle.

This possibly wasn't working before merging. I don't see amp validator-cpp being run in this PR's checks :/ that's on infra for missing the build target
https://app.circleci.com/pipelines/github/ampproject/amphtml/26964/workflows/78253ef9-8f46-45c2-a6ac-ddd7b8df12f4/jobs/564510