Request for a threadless activity indicator

[rwols]

The current ActivityIndicator spawns a thread. There is some noticeable overhead associated with this thread. I'm noticing some stuttering when the indicator starts. Would it be possible to have a design that utilizes the assumption that the main thread is never blocked?

[rchl]

I did make a main-thread variant in sublimelsp/lsp_utils#47 just to see if it performs well and I don't see it causing any blocking issues or even registering on the Profile plugins view.