"Unchanged files with check annotations" is disruptive and should be configurable

The "Unchanged files with check annotations" feature when using problem matchers needs to be configurable (for each action/matcher): It's pretty discouraging for a new contributor to see loads of unrelated warnings from a style checker in their first PR that are completely unrelated, not to mention that it also adds noise for checkers where you know that it's not something that could be caused in changes from another file in the PR.

For example, I'm running stylelint with no-descending-specificity warnings enabled. For CSS added in a PR those warnings may be useful, but I REALLY don't care about the almost 1000 warnings in our existing codebase (some even in legacy files) when running CI for a new PR!

Right now the only workaround for this is to either disable the rule altogether, only show errors but not warnings, or somehow only run the linter on new/changed files when running the action for a PR.

No file or test is named. Start by locating the GitHub Actions Toolkit handling for problem matchers and the “Unchanged files with check annotations” behavior, then review the issue discussion for configuration expectations. Done means allowing the behavior to be configured separately for each action or matcher without requiring warnings to be disabled globally.