"silent" severity items showing up

[felschr]

Using the new .editorconfig integration, I noticed that items with severity set to silent & suggestion still show up.
I guess suggestions are probably intended to show up but silent items definitely shouldn't.
The same config works fine with omnisharp-vscode.

[nickspoons]

silent items are tricky. They are returned as LogLevel: Hidden from O#roslyn, and we did attempt to always hide these at one point. However this turned out to be a mistake, because some diagnostics always appear to be marked as Hidden, for example "unnecessary usings", see #497

suggestion diagnostics are returned as LogLevel: Info from O#roslyn and are given the location type value I which ALE interprets as Information, so these are generally marked differently by ALE. silent/Hidden diagnostics are given the location subtype value Style which ALE also can mark differently.

To have diagnostics hidden completely, we currently rely on the g:OmniSharp_diagnostic_overrides dictionary.