Language server changes

[udoprog]

This pull request significantly improves handling of multiple sources in the language server and adds workspace support.

Emitting diagnostics have been reworked, so that it should be less likely to get stuck in a state where diagnostics is never removed.

Workspace support has also been added in the language server. A workspace is triggered if a Rune.toml file is found at the root of the workspace. The sources associated with a workspace are always collected and processed by the language server.

On top of this, any sources you open up will be handled as normal entrypoints unless they are part of a workspace.

This means we can finally deal with non-trivial project topologies and most improtant modules. With the caveat that these must have an associated Rune.toml file which points out the entrypoint.

Workspace configuration also comes with its own diagnostics:

Hovering over the rune-languageserver bottom left option reveals a few controls:

Stopping the server prevents it from running at all (during this session) in case there are any issues.

[udoprog]

This is all part of rune-vscode 0.12.7 for anyone who wants to take it for a spin. It should automatically download the latest nightly languageserver which comes with all the listed improvements.