Yabridge integration

Enhancement Summary

I feel it would be a good idea to integrate yabridge vst host into the lmms codebase. I discussed this on discord but didn't get much feedback and also, this one looks worthy of an issue.

The way I imagine the execution is for yabridge to be a submodule (or a dependency, whichever is better) which will be built as a plugin (but only for linux systems because it's linux only).

Justification

I am suggesting yabridge to be a vestige/current vst implementation replacement as the way we handle vst is very buggy (almost 40% of our bug reports come from vst issues if I'm right). We can keep our current implementation for backwards compat but imo, it should be phased out in favour of a better system.

Also, i know carla exists but even carla is buggy.

Another advantage I see is slimmer vst code and concentrate our vst implementation to windows alone (or use a bridge there too)

The issue names no files, tests, or entry points. Start by reviewing LMMS's existing VST implementation and yabridge's Linux-only plugin or dependency requirements, then define the integration and backwards-compatibility boundaries. Done would require an agreed, buildable Linux integration plan rather than only a proposal.