R1:3bea3fbb1289

When computing revision ownership, cache some intermediate results for performance

Summary:
Ref T12319. With large datasets, the computation of which packages own paths in a revision is needlessly slow.

Improve performance through caching:

- Cache which paths belong to each repository.
- Cache the split fragments of each path.
- Cache the path fragment counts.
- Micro-optimize accessing `$this->path`.

Test Plan:
- Used `bin/lipsum` to generate 4,000 packages with 150,000 paths.
- Created a…