Option to show source in diagnostic picker

[rafamadriz]

Is your feature request related to a problem? Please describe.
When there's multiple servers attached, and opening diagnostics picker, I don't know which diagnostic is coming from which server.

Describe the solution you'd like
Add option to diagnostic picker to show source.

Describe alternatives you've considered

Additional context
There's issue #2110 that proposes to directly append the source to diagnostic message, but I think it's better to add it as an option

[jamestrew]

Should be fairly simple. I can take a look at this over the next week or so.

[shashanktomar]

Hey Folks, any update on this?