[Common] Improve performance of FulfillsITSHitRequirements

[ktf]

Use a bitmask rather than an std::set.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 44 warnings, 🔕 0 disabled

[ktf]

@ddobrigk can you please have a look also here? This also pops up in the profiles.

[alibuild]

Error while checking build/O2Physics/o2 for 46de008 at 2026-05-30 07:08:

## sw/BUILD/O2Physics-latest/log
c++: fatal error: Killed signal terminated program cc1plus
c++: fatal error: Killed signal terminated program cc1plus
ninja: build stopped: subcommand failed.

Full log here.

[ktf]

@dsekihat any reason why this is not merged? Any reason for the TrackSelection class to have a dictionary, BTW?

[dsekihat]

Dear @ktf , My fault. I overlooked the automatic notification. It is merged just now.