See flutter/engine#51325.

Before flutter/engine#50844, when golden_tests_harvester was invoked in a release builder (i.e. where isLuci evaluates to true, but SkiaGoldClient.isAvailable evaluates to false), it would just ... party on, seemingly producing no errors. I'm not sure exactly how.

Personally, I don't think a tool should "pretend" to run as a silent behavior, that is, if it's invoked, it should run.

Ideas:

1. Embrace Conditionally run golden_tests_harvester for run_impeller_golden_tests. engine#51325, and panic if executed without GOLDCTL. Probably tear-out the FakeSkiaGoldClient stuff.
2. Add a flag (--dry-run or similar) that makes this explicit versus implicit. Even --dry-run-if-gold-ctl-omitted is better.
3. Embrace chaos and close this PR as WAI.