* Rework how markdown server works with documents
This rewrites how the markdown server works with documents. The goal is to better handle switching between in-memory versions of a doc (from `TextDocument`) and versions of the same doc on disk. From the markdown service's POV, there is only one type of document
As part of this, I've also adopted the newest markdown language service version
* Bump package-lock versions
For #159805
This splits the markdown server into two main functions:
- `startVsCodeServer` which assumes the client can implement all the functionality of VS Code. It is not specific to VS Code however, the client just need to implement the custom messages that VS Code does
- `startServer` which lets you pass in your own implementation of the parser and workspace. A consumer of the server can then use this to have their own custom server implementation, which might use normal node apis to read files
* Move MD diagnostics to language server
This switches us to using the LSP pull diagnostic model with a new version of the language service
* Bump package version
* Delete unused file
