Adds a lsp_save_all function

[fserb]

We also fix open_file to avoid focusing the view if the file is already open.

This fixes #1849

[fserb]

done :)

[fserb]

Fixed lint error.

[rchl]

I think there is a pretty fundamental issue with this approach.

This will trigger save actions for all changed files at once. And a save action is only allowed to run for a certain amount of time (by default 2s). If we start all the save actions for all files at the same time, there is a very high chance that many of those will time out since all actions will try to run at the same time but will be blocked by each other since all run in the same thread. Timing out means that the formatting on save or code actions on save might not get applies (the file will still be saved after the timeout).

I don't know how serious this issue would be in practice. It very much depends on the number of files to save and the servers used...

Possibly the solution here could be to increase the timeout per lsp_save command triggered. Maybe to even 10s.

[rchl]

With that said, if others are fine with that potential issue, I'm not gonna block this from being integrated. It could be improved later.

Though for the purpose of visibility, I'd ask you to also add the new command to the default key bindings, commented out.

[fserb]

Added keymap.

[rwols]

Is anyone against merging this?