[CI] Skip irrelevant builds on desktop files changes

Summary: I've noticed that we are using paths-ignore option on GitHub CI, so I added desktop/** to CIs which shouldn't be affected by changes in the desktop workspace.

Test Plan: Tested on a fork if the CI still runs on changes outside of the desktop and doesn't run when the only changes are in the desktop.

Reviewers: atul, varun, tomek

Reviewed By: atul

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D6144