feat: add support for m.call.invite events in the timeline and as a last room message

[stefanceriu]

Prompted by element-hq/element-x-ios#1837

This PR exposes m.call.invite events on the Timeline and as a latest Room message. It will allow the client to render them and inform the user accordingly.

[bnjbvr]

Nice!

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 30.76923% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 83.83%. Comparing base (4b711e4) to head (dc09e98).
Report is 1 commits behind head on main.

❗ Current head dc09e98 differs from pull request most recent head d9b4623. Consider uploading reports for the commit d9b4623 to get more accurate results

Files	Patch %	Lines
...trix-sdk-ui/src/timeline/event_item/content/mod.rs	0.00%	6 Missing ⚠️
crates/matrix-sdk-ui/src/timeline/event_handler.rs	0.00%	2 Missing ⚠️
crates/matrix-sdk-ui/src/timeline/mod.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3181      +/-   ##
==========================================
- Coverage   83.85%   83.83%   -0.03%     
==========================================
  Files         232      232              
  Lines       23941    23952      +11     
==========================================
+ Hits        20076    20079       +3     
- Misses       3865     3873       +8     

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[stefanceriu]

Noice, thanks for the review! 🙌

Feel free to merge it whenever you get around to it.