fix(event_cache): store correct encryption information for local echoes

[stefanceriu]

This patch exposes one's underlying EncryptionInfo used when sending raw Room events, uses it to create a DecryptedRoomEvent and corresponding TimelineEvent, and correctly populates the EventCache with local echoes.

[poljar]

We can tweak this a bit more to make it more correct, also a regression test for this would be very welcome.

[codecov]

Codecov Report

❌ Patch coverage is 90.52632% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.50%. Comparing base (29b693e) to head (7b0d49c).
⚠️ Report is 11 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-crypto/src/machine/mod.rs	88.57%	4 Missing ⚠️
...ates/matrix-sdk/src/encryption/identities/users.rs	50.00%	0 Missing and 1 partial ⚠️
crates/matrix-sdk/src/room/futures.rs	83.33%	0 Missing and 1 partial ⚠️
crates/matrix-sdk/src/room/mod.rs	0.00%	0 Missing and 1 partial ⚠️
crates/matrix-sdk/src/send_queue/mod.rs	95.45%	0 Missing and 1 partial ⚠️
crates/matrix-sdk/src/widget/matrix.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5936      +/-   ##
==========================================
- Coverage   88.50%   88.50%   -0.01%     
==========================================
  Files         362      362              
  Lines      103351   103399      +48     
  Branches   103351   103399      +48     
==========================================
+ Hits        91469    91511      +42     
- Misses       7534     7540       +6     
  Partials     4348     4348              

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

[codspeed-hq]

CodSpeed Performance Report

Merging #5936 will not alter performance

_{Comparing stefan/localEchoEncryptionInfo (7b0d49c) with main (b98a832)}

Summary

✅ 50 untouched

[stefanceriu]

Okay, I went ahead and rewrote most of this based on the last idea.

[poljar]

Alright, this looks good. Very nicely done.

Can we just get appropriate changelog entries for the main crate and the crypto crate.

Furthermore, a regression test for this would be very nice.

[poljar]

Took a bit of time to figure out why things weren't working, but we got there.