Add mesonlsp

[JCWasmx86]

This adds the C++-Rewrite of Swift-MesonLSP as a separate mesonlsp server. Swift-MesonLSP users will be upgraded to mesonlsp. If there are regressions, users can fallback to Swift-MesonLSP-legacy.

Issues:

• Switching language at runtime doesn't work.
• Not sure what to do with the options (Copy paste a old?)
• Not sure whether the changes to yarn.lock are needed
• I'm not sure how to make this code less hacky

And important: Before this language server is rolled out, I would like to ask adventurous people for feedback. Sure mesonlsp is perfect for my usage of meson and the usage of tristan957 (Thanks for testing!), but I think it's important to first roll it out to e.g. 10 users (That have installed mesonlsp by themselves and then continue with the entire rollout

[JCWasmx86]

Please don't merge yet... I have to test it a bit more on Windows

[tristan957]

I would recommend just dropping the old server. VSCode allows pinning an extension if people really want it

[JCWasmx86]

This is not because people e.g. prefer Swift-MesonLSP, but for example if there are any severe regressions in mesonlsp (Especially on Windows, as I didn't test it that much compared to Linux) people can easily switch back.

In a few months we could drop the old language server.

[tristan957]

I still think that is where pinning comes into play

[JCWasmx86]

I've removed all traces of Swift-MesonLSP, except that it is an alias for mesonlsp to avoid any migration difficulties. Furthermore I will release a new version today that improves cross-platform support of features (Windows now supports formatting, too)

[JCWasmx86]

@tristan957 Could you please review this change, if possible as it contains important patches