chore(ffi): use ruma's built-in uniffi support for power levels

[Johennes]

This is the smallest possible way that I could find to start using ruma/ruma#2338 in the FFI bindings. It doesn't really improve much on its own because the types that were replaced here are still used elsewhere. I thought it'd be good to start small though.

The only difference of the two types in the foreign language should be the use of Custom vs. Other.

• Public API changes documented in changelogs (optional)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.80%. Comparing base (70665a8) to head (5acec1d).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6161   +/-   ##
=======================================
  Coverage   89.79%   89.80%           
=======================================
  Files         365      365           
  Lines      100469   100469           
  Branches   100469   100469           
=======================================
+ Hits        90215    90224    +9     
+ Misses       6721     6714    -7     
+ Partials     3533     3531    -2     

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[codspeed-hq]

Merging this PR will not alter performance

✅ 50 untouched benchmarks

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_{Comparing Johennes:johannes/uniffi (5acec1d) with main (70665a8)}

[Johennes]

This is failing the complement-crypto tests now. These downgrade uniffi to 0.28.3. This no longer works because ruma's new uniffi support depends on changes from uniffi 0.31.0.

In particular:

• doc(hidden) doesn't work in 0.28.3
• uniffi::export only works on functions and impl blocks in 0.28.3 (ruma uses uniffi::export(Display, Eq, Hash) on an enum)
• In 0.28.3 custom_type! only takes two type parameters and then you need to implement UniffiCustomTypeConverter. In 0.31.0 the macro takes the converters directly in a third argument

I can think of the following ways to resolve this:

1. Split the uniffi implementation in ruma into two features, one that works with 0.28.3 and one that uses 0.31.0
2. Change the rebuild_rust_sdk.sh script from complement to hack the changes into a local ruma checkout

I'm not sure which of these is worse but maybe I've missed a better option?

[jplatte]

The better option is to help move NordSecurity/uniffi-bindgen-go#86 forward, IMHO.

[Johennes]

The better option is to help move NordSecurity/uniffi-bindgen-go#86 forward, IMHO.

That's still two minor versions behind what ruma needs but, yes, ideally the complement crypto tests wouldn't have to downgrade uniffi in the first place.

[jplatte]

Yeah, but it would unblock additional upgrades (which may be much easier than that one, if you're lucky ^^).