Handle window/showMessage and display it bellow status line

[ayoub-benali]

This feature is also hidden behind the display-messages setting which is used for displaying Progress.

I don't think it make sense to create separate setting for this feature as I don't expect a server to send both Progress and window/showMessage but I can add one if you prefer.

Metals relies on this notification for providing info about the build and is configured here.

Hopefully this will be useful for other language servers.

Here is an example (bottom left) for the message sent by Metals.

Fix https://github.com/helix-editor/helix/issues/5524

[ayoub-benali]

What should be the new setting name ? Progress is already using a missleading name. should I introduce a breaking change and make progress be controlled with 'display-progress-message' while show message would use the current name ?

[the-mikedavis]

Yeah I think you're right about the names. Ideally we should avoid breaking changes but I think progress messages would be better as display-progress-messages and showMessage messages as display-messages.

[ayoub-benali]

@the-mikedavis So I made the change but I think now a R-breaking-change label should be added to the PR, I couldn't do it myself.

[ayoub-benali]

@the-mikedavis Is the popup support a must have for this PR or could we added it later depending on the user requests ? I think statusline is already better than nothing, since this LSP notification isn't even supported now

[igor-ramazanov]

Can we include this into the next release?

[AlexanderBrevig]

(sorry, I thought I was in another PR - still, I really do want this :) would make it a bit easier to use Helix as a client for testing new LSPs 👍🏻)