refactor(sdk): Put ruma-federation-api dependency behind a feature

[zecakeh]

In theory clients shouldn't make requests to the server-server API. A way to work around it for this specific case would be to implement MSC4383.

In the meantime, clients that don't want to use Client::server_vendor_info() won't have to build the extra dependencies added by ruma-federation-api.

The feature is enabled for the bindings, so it isn't a breaking change for matrix-sdk-ffi.

An alternative way to avoid the extra dependencies would be to implement the endpoint in the SDK directly, since the extra dependencies of ruma-federation-api are not necessary for this endpoint. See also the discussion at https://matrix.to/#/!2Z7UlDlK4gFTCIiy2kotE0pyXM2qNp7228PZr9b87Y0/$oEV-B5fPMBgVg3JOR1Qy83DFWVyEcidfdGB0yeE0t8U?via=matrix.org&via=element.io&via=ahouansou.cz.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.66%. Comparing base (73449f4) to head (e324e77).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5912      +/-   ##
==========================================
- Coverage   88.66%   88.66%   -0.01%     
==========================================
  Files         362      362              
  Lines      104399   104399              
  Branches   104399   104399              
==========================================
- Hits        92569    92564       -5     
- Misses       7499     7502       +3     
- Partials     4331     4333       +2     

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[codspeed-hq]

CodSpeed Performance Report

Merging #5912 will not alter performance

_{Comparing zecakeh:federation-api-feature (e324e77) with main (73449f4)}

Summary

✅ 50 untouched