Restart language server when changing document language

[the-mikedavis]

Document::set_language currently only changes the syntax and highlighting parts of a document. If the language server configuration or binary changed, the language server is not terminated or restarted. For example, :set-language text on a rust file running rust-analyzer will not close the rust-analyzer session - you will still see completion and diagnostics.

Unless the language server configuration is the same before and after, Document::set_language should close the open language server (if any) and start the new language server for the new configuration.

(In the long-run, we may also want to look into using didChangeConfiguration for language servers that support it. ref)

[the-mikedavis]

Document::set_language should also probably call Document::detect_indent_and_line_ending since those values can change when the Document.language field changes

[pascalkuthe]

I think this can be closed, see #8949 (comment)

In these sense that all callsites habdle this so thisndoesnt lead to any issues observaböe by users