refactor: evaluate usage of `--only-changed` for playwright tests

[mfranzke]

Due to the introduction of --only-changed parameter, we should evaluate to optimize our pipelines (assumption: via lint-staged):
microsoft/playwright#15075 (comment)

[nmerget]

It might be a good idea to use this, but it only checkes for changes inside the .spec.ts file. We don't touch those files in general, so the test wouldn't run. What we change are the showcases/components and the cli option wouldn't recognize a change in it. We introduced this PR which will reduce the amount of tests, that's all we can do in our use case