feature: send voice message API

[alfogrillo]

This PR adds a ffi binding for sending voice messages in the legacy format (before extensible events). It also makes minor changes in the matrix-sdk crate to accomodate this change.

[jplatte]

You can undo the latest commit now and run cargo update -p ruma-events instead to get a crates.io version that includes the new constructors.

[alfogrillo]

You can undo the latest commit now and run cargo update -p ruma-events instead to get a crates.io version that includes the new constructors.

Thanks.
Done here.

[codecov]

Codecov Report

Attention: 22 lines in your changes are missing coverage. Please review.

Comparison is base (ba2a513) 78.77% compared to head (c4ab772) 78.72%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2697      +/-   ##
==========================================
- Coverage   78.77%   78.72%   -0.05%     
==========================================
  Files         200      200              
  Lines       20359    20371      +12     
==========================================
  Hits        16037    16037              
- Misses       4322     4334      +12     

Files	Coverage Δ
crates/matrix-sdk/src/attachment.rs	32.85% <0.00%> (-1.48%)	⬇️
crates/matrix-sdk/src/encryption/mod.rs	53.12% <0.00%> (ø)
crates/matrix-sdk/src/media.rs	59.18% <0.00%> (-5.99%)	⬇️

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[bnjbvr]

woooo voice messages \o/ Gen Z thanks you for your duty.

[bnjbvr]

Thanks!