Drop support for Node 8; Require Node 10+ (#7650)

* Require Node 10+ for cli engine

* update chalk to latest (requires Node 10+)

* Update execa to latest

* Update cli-table3 to latest (required Node 10+)

* Update log-symbols (requires Node 10+)

* Update tmp dep (requires Node >=8.17.0)

* Update fs-extra dep (requires Node 10)

* Update mock-fs to 4.12.0

* increase circle base image to node 10

* fix flaky firefox test

* make job names consistent

* reconfigure percy parallelism, finalize percy after running visual jobs, remove separate desktop-gui-visual-tests job

* rename job correctly

Co-authored-by: Brian Mann <brian.mann86@gmail.com>