feat(sdk-crypto): Add Identity based room key sharing strategy

[BillCarsonFr]

~~Draft because based on https://github.com/matrix-org/matrix-rust-sdk/pull/3605~~ Fixes https://github.com/matrix-org/matrix-rust-sdk/issues/3563

This PR just introduce a new way to distribute room keys based on identities, by only sharing with devices signed by their owner. This is a first PR to introduce this mode, but it will be really usable once we introduce some support for identity TOFU.

• [ ] Public API changes documented in changelogs (optional)

Signed-off-by:

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.47619% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.87%. Comparing base (ca6537b) to head (9294618). Report is 138 commits behind head on main.

Files	Patch %	Lines
...c/session_manager/group_sessions/share_strategy.rs	85.71%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3607      +/-   ##
==========================================
+ Coverage   83.86%   83.87%   +0.01%     
==========================================
  Files         254      254              
  Lines       25892    25909      +17     
==========================================
+ Hits        21714    21731      +17     
  Misses       4178     4178              

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