feat: add QQmlImageProviderBase

[dphaldes]

supercedes #1142

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (71eee5f) to head (e091394).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1430   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           75        75           
  Lines        13457     13457           
=========================================
  Hits         13457     13457           

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[dphaldes]

I have "working" implementation here https://github.com/dphaldes/compose/blob/master/src/bridge.rs.

Not particularly fond of the solution since it uses an unchecked cast since I wasn't able to figure out how to cast Pin<&mut QQmlImageProviderBase> into *mut QQmlImageProviderBase. The application also segfaults when closing probably because it is trying to release the ImageProvider.

Any ideas appreciated!