[TomasVotruba]

Folds the UsedSkipCollector used-skip tracking into Skipper, so there is a single skipper service instead of two.

• Skipper now owns the usedSkips state, with a private markUsed() and a public provideUsedSkips().
• PathSkipper::shouldSkip() no longer marks skips used; it is renamed to matchSkippedPath() and returns the matched path (or null). Skipper::shouldSkipFilePath() does the marking. This breaks the Skipper -> PathSkipper -> Skipper dependency cycle the merge would otherwise create.
• FilesFinder routes path skips through Skipper::shouldSkipFilePath() so finder-level path skips stay marked used.
• ApplicationFileProcessor reads used skips from Skipper directly.
• UsedSkipCollectorTest is merged into SkipperTest.