Feature request: lsp-ui-sideline for all errors and warning not only the ones that is hovered

[Ghibranalj]

It would be nice to have a boolean variable to enable showing all errors. It would be something like virtual text in neovim.

Something like this:

[zjp]

I opened a duplicate issue about this a few weeks ago, but closed it when I became aware of this issue. I'm working on an implementation of this here: https://github.com/zjp/lsp-ui/tree/show-all-diagnostics

Current issues:

If you have hl-line mode on the hightlight disappears between the end of the line you're on and the diagnostic

It looks funny to have diagnostics on lines the point is not on be shown above their lines. You can choose to show them on the same line as the sideline markers, but if a line has multiple diagnostics to show, one diagnostic will be shown and the rest of the diagnostics disappear (you can see this in action by bringing line 372 of lsp-ui-sideline.el into view).

It's really annoying to have the diagnostics flicker on every motion, so when showing all diagnostics they're supposed to update only when the contents of the buffer change. For some reason, sometimes you can get duplicated messages.