R1:da7d92dd0a4e

Catch more HTTP VCS errors and convert them into VCS repsonses

Summary:
Ref T13590. Currently, errors arising from cluster locking (like the "stuck write lock" exception) are not caught and converted into VCS responses on the HTTP VCS workflow.

Catch a broader range of exceptions and convert them into appropriate responses.

Test Plan:
- Forced a "stuck write lock" exception, pushed to a Git repository over HTTP.
- Before: generic fatal.
- After: VCS-specific fatal with a useful message in the "X…