refactor(base): Use PossiblyRedactedStateEventContent bound in MinimalStateEvent

[zecakeh]

We usually don't care if the event was redacted or not, we usually want to know whether a field is set or not, so we don't need Original and Redacted variants.

This simplifies several parts of the code since we don't have to handle the intermediate enum to access the content now. Due to new APIs in Ruma we can also just convert original and redacted event contents to possibly redacted event contents.

This should allow further code removal in a follow-up PR, by allowing to use the same code to handle Sync* and Stripped* events in RoomInfo.

The backwards-compatible deserialization of MinimalStateEvent was verified in a client with Fractal.

[codecov]

Codecov Report

❌ Patch coverage is 79.83871% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.90%. Comparing base (87ce49e) to head (e5005b7).
⚠️ Report is 12 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-base/src/utils.rs	80.00%	13 Missing ⚠️
crates/matrix-sdk-base/src/room/room_info.rs	85.71%	4 Missing and 1 partial ⚠️
crates/matrix-sdk-base/src/room/create.rs	0.00%	4 Missing ⚠️
...x-sdk-base/src/response_processors/state_events.rs	0.00%	0 Missing and 1 partial ⚠️
crates/matrix-sdk-base/src/room/tombstone.rs	75.00%	0 Missing and 1 partial ⚠️
crates/matrix-sdk-base/src/store/ambiguity_map.rs	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6088      +/-   ##
==========================================
+ Coverage   89.83%   89.90%   +0.06%     
==========================================
  Files         360      360              
  Lines       99873    99789      -84     
  Branches    99873    99789      -84     
==========================================
- Hits        89723    89712      -11     
+ Misses       6641     6575      -66     
+ Partials     3509     3502       -7     

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing zecakeh:room-info-possibly-redacted (e5005b7) with main (911b559)}

Summary

✅ 50 untouched benchmarks

[zecakeh]

Note: I would have preferred to be able to serialize this directly without a tag, but for some reason applying #[serde(untagged)] on a variant of the deserialization helper makes the deserialization of the join rules content fail.