Update dart_skills_lint dependency to e449787 and inherit target configuration (#9830)

Updates the pinned `dart_skills_lint` reference in `tool/pubspec.yaml` to commit hash `e4497873950727ee781fa411c1a2f624b1ec50c6` (version `0.3.0`). Refactors `tool/test/validate_skills_test.dart` to load configuration dynamically via `ConfigParser.loadConfig` and omit targeting overrides, enabling native path inheritance from `tool/dart_skills_lint.yaml`.
### General checklist
### Issues checklist
### Tests checklist
### AI-tooling checklist
    * [x] I read the [AI contributions guidelines] and agree to follow them.
    * [x] I reviewed all AI-generated code before opening this PR.
    * [x] I understand and am able to discuss the code in this PR.
    * [x] I have verifed the accuracy of any AI-generated text included in the PR description.
    * [x] I commit to verifying the accuracy of any AI-generated code or text that I upload in response to review comments.
### Feature-change checklist 
    * [x] I added the `release-notes-not-required` label or left a comment requesting the label be added.