deps: upgrade gax to 2.7.1, protobuf to 3.19.1, grpc to 1.42.1, and truth to 1.1.2, upgrade Bazel in GitHub Actions, and fix build error

[chanseokoh]

The versions are aligned with those in gax-java.

Also, builds were failing for the same reason we observed in gax-java. Applying the same fix to use PROTOBUF_MAVEN_ARTIFACTS.

The CI change: Bazel version in the container is old, so builds fail with these changes. We encountered the same error on gax-java, and the J-Team had a discussion around this. ubuntu-latest comes with a recent Bazel, and we didn't find a good reason to use a custom image. We came to the agreement that we would just use ubuntu-latest.

[chanseokoh]

Oops, something wrong. Will fix it.

[chanseokoh]

Turns out the protobuf dependency is conditionally loaded via the custom _maybe method, only when it has not been loaded previously.

def _maybe(repo_rule, name, strip_repo_prefix = "", **kwargs):
    if not name.startswith(strip_repo_prefix):
        return
    repo_name = name[len(strip_repo_prefix):]
    if repo_name in native.existing_rules():
        return
    repo_rule(name = repo_name, **kwargs)

All in all, the build will start building successfully once we make a new release of gax-java and update WORKSPACE in this repo to use that version. Will leave this open until then.

[codecov]

Codecov Report

Merging #875 (9c57546) into main (7c76256) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #875   +/-   ##
=======================================
  Coverage   87.84%   87.84%           
=======================================
  Files         153      153           
  Lines       15966    15966           
  Branches     1155     1155           
=======================================
  Hits        14025    14025           
  Misses       1601     1601           
  Partials      340      340           

Impacted Files	Coverage Δ
...omposer/rest/HttpJsonServiceStubClassComposer.java	52.94% <ø> (ø)

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[chanseokoh]

@meltsufin fixed all issues. Ready for review.

[chanseokoh]

@vam-google I'm syncing the versions with those in gax-java. Any concern?

[vam-google]

LGTM