fix(ci): reorder gke tags and labels variable expansions

[BradLugo]

Description

If you're really unlucky, you can get a . at the end of the tags variable, which will be substituted for - after we replace the last - with x. GKE doesn't allow for - at the end of the string, which is why we change the last -.

See https://github.com/openshift/release/pull/47789 for a real-world example of this problem.

These changes reorders the shell expansion so we first replace all . with -, then delete the last -.

Cherry-picked from https://github.com/stackrox/scanner/pull/1513

Testing Performed

Testing the variable expansions:

# Before
❯ JOB_NAME=rehearse-47789-pull-ci-stackrox-scanner-release-2.32-e2e-tests
❯ tags="stackrox-ci"
❯ tags="${tags},stackrox-ci-${JOB_NAME:0:50}"
❯ echo "${tags}"
stackrox-ci,stackrox-ci-rehearse-47789-pull-ci-stackrox-scanner-release-2.
❯ tags="${tags/%-/x}"
❯ echo "${tags}"
stackrox-ci,stackrox-ci-rehearse-47789-pull-ci-stackrox-scanner-release-2.
❯ tags="${tags//./-}"
❯ echo "${tags}"
stackrox-ci,stackrox-ci-rehearse-47789-pull-ci-stackrox-scanner-release-2-

# After
❯ JOB_NAME=rehearse-47789-pull-ci-stackrox-scanner-release-2.32-e2e-tests
❯ tags="stackrox-ci"
❯ tags="${tags},stackrox-ci-${JOB_NAME:0:50}"
❯ tags="${tags//./-}"
❯ tags="${tags/%-/}"
❯ echo "${tags}"
stackrox-ci,stackrox-ci-rehearse-47789-pull-ci-stackrox-scanner-release-2

[openshift-ci[bot]]

@BradLugo: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-tests	1df1326f8b1a10fa89953a9cddd5ce0cebdc345d	link	false	/test e2e-tests
ci/prow/push-images	1df1326f8b1a10fa89953a9cddd5ce0cebdc345d	link	true	/test push-images
ci/prow/store-genesis-dump	1df1326f8b1a10fa89953a9cddd5ce0cebdc345d	link	false	/test store-genesis-dump
ci/prow/images	1df1326f8b1a10fa89953a9cddd5ce0cebdc345d	link	true	/test images
ci/prow/slim-e2e-tests	1df1326f8b1a10fa89953a9cddd5ce0cebdc345d	link	false	/test slim-e2e-tests
ci/prow/store-db-dump	1df1326f8b1a10fa89953a9cddd5ce0cebdc345d	link	false	/test store-db-dump

Full PR test history. Your PR dashboard.

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[BradLugo]

O.B.E - we're only supporting this change for 2.34+