CI: Strip binaries produced by setup-test-env

What does this MR do and why?

This reduces artifact's size from 321 MB to 202 MB.

Refs: #442029 (closed)

Draft?

• [-] Create a new label to act as killswitch for stripping binaries:
  • ~pipeline:debug-binaries or pipeline:binaries-not-stripped
• Document how to disable binary stripping

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Verify on CI

Stripped

https://gitlab.com/gitlab-org/gitlab/-/jobs/6180165325/artifacts/download contains an artifact of 202 MB size (previously 321 MB).