feat(sdk): Use state_after in sync v2

[zecakeh]

It is supposed to be an improvement over state, since it allows the
server to send updates to the state that might not be reflected in the
timeline.

This is also the same behavior as in Simplified Sliding Sync.

This is MSC4222 that was accepted and is about to get merged in the spec.

[codspeed-hq]

CodSpeed Performance Report

Merging #5488 will not alter performance

_{Comparing zecakeh:state-after (329151c) with main (787861e)}

Summary

✅ 31 untouched benchmarks

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.94%. Comparing base (787861e) to head (329151c).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...x-sdk-base/src/response_processors/room/sync_v2.rs	84.37%	3 Missing and 2 partials ⚠️
crates/matrix-sdk/src/widget/matrix.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5488      +/-   ##
==========================================
+ Coverage   88.93%   88.94%   +0.01%     
==========================================
  Files         335      335              
  Lines       93274    93262      -12     
  Branches    93274    93262      -12     
==========================================
+ Hits        82949    82956       +7     
+ Misses       6462     6444      -18     
+ Partials     3863     3862       -1     

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[andybalaam]

Looks good, with a couple of questions and suggestions.