R1:df1e9ce646c0

Treat Owners paths like "/src/backend" and "/src/backend/" identically

Summary:
Depends on D19183. Ref T11015. Currently, adding a trailing slash works great and omitting it mysteriously doesn't work.

Store a normalized version with an unconditional trailing slash for the lookup logic to operate on, and a separate display version which tracks what the user actually typed.

Test Plan:
- Entered "/src/main.c", "/src/main.c/", saw them de-duplicate.
- Entered "/src/main.c", saw it stay that way in the…