fix: use dynamic registrations and start project node asynchronously

[doorgan]

After we transitioned to GenLSP, I was no longer able to make Expert work with the Lexical vscode extension, so I would only be able to test it with neovim.

Apparently this is caused by two issues:

• Because we weren't doing the dynamic registrations when receiving the Initialized notification but rather in the initialization request, vscode stopped sending requests to the server
• I don't fully understand why, but if we start the project node synchronously on initialization, genlsp will apparently stop handling requests/notifictations from the vscode client, causing the client to cancel every request.

Fixing those two things I got Expert fully working on vscode again. I accidentally found those fixes while working on workpsace folders support, where the project nodes are started when files are opened instead of on initialization.