feat: Add support for MSC4471 event streams

[bradtgmurray]

Added an initial implementation of a portion of MSC4471. Included in this pull request is the the matrix-sdk changes, validated by unit tests. Not included in this pull request is changes to matrix-sdk-ui, which I figured would be best done as a follow up to keep this original PR a reasonable size. Also, encryption of the stream events is not yet implemented, again to manage the size of this initial PR.

This MSC has not been merged, but I'd like to use matrix-rust-sdk as a testing ground for it.

My experience with Rust is rather light, and I did use AI to assist me in writing this PR, but I did quite a bit of iteration to make something that looks reasonably good to my inexperienced eyes. Feedback is greatly appreciated!

• I've documented the public API changes in the appropriate changelog files
• This PR was made with the help of AI.

NOTE: This pull request isn't mergable as is as it's dependant on me adding the appropriate types to Ruma. Unfortunately, it looks like Ruma does not permit AI-assissted changes, so my work isn't mergable as is. I would love some advice on how to proceed on that front. For now, this branch has adjusted the dependency to point to my fork of Ruma, but that is obviously not a good idea to merge like that.

Signed-off-by: Brad Murray bradtgmurray@gmail.com

[codspeed-hq]

Merging this PR will not alter performance

✅ 50 untouched benchmarks

---

_{Comparing bradtgmurray:msc4471-event-streams (0836539) with main (1205c2b)}

[codecov]

Codecov Report

❌ Patch coverage is 64.63211% with 423 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.68%. Comparing base (1205c2b) to head (0836539).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/matrix-sdk/src/event_streams/publisher.rs	54.34%	253 Missing and 10 partials ⚠️
...rates/matrix-sdk/src/event_streams/subscription.rs	84.76%	70 Missing and 8 partials ⚠️
crates/matrix-sdk/src/room/event_streams.rs	0.00%	60 Missing ⚠️
crates/matrix-sdk/src/event_streams/mod.rs	55.81%	16 Missing and 3 partials ⚠️
crates/matrix-sdk/src/client/mod.rs	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6607      +/-   ##
==========================================
- Coverage   89.96%   89.68%   -0.28%     
==========================================
  Files         382      386       +4     
  Lines      107971   109167    +1196     
  Branches   107971   109167    +1196     
==========================================
+ Hits        97136    97911     +775     
- Misses       7167     7574     +407     
- Partials     3668     3682      +14     

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