refactor: Rename TimelineMetadata::all_events to all_remote_events

[Hywan]

This patch renames the all_events field to all_remote_events in TimelineMetada for the sake of clarity.

---

• Address [meta] EventCache storage #3280

[bnjbvr]

Makes sense, feel free to rename add_or_update_event to add_or_update_remote_event too if you'd like (and don't think the name's too long 🙃)

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 6 lines in your changes missing coverage. Please review.

Project coverage is 85.09%. Comparing base (ad3d1fb) to head (d1f7e5c).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
...tes/matrix-sdk-ui/src/timeline/controller/state.rs	78.57%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4366      +/-   ##
==========================================
- Coverage   85.09%   85.09%   -0.01%     
==========================================
  Files         280      280              
  Lines       30547    30558      +11     
==========================================
+ Hits        25995    26003       +8     
- Misses       4552     4555       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.