fix(gatsby-dev-cli): wait for files to be copied before exiting (#8387)
fix(gatsby-dev-cli): wait for files to be copied before exiting (#8387)

* fix: increase debounce threshold in CI environments

* fix: use Promise.all to ensure copies/quitting works more smoothly

* fix: change strategy for watching; watch an array, and listen to ready

* chore: remove syspath naming stuff

* chore: add comment re: ready event

* chore: make a change to trigger e2e tests

gatsbyjs/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,0x80/gatsby,0x80/gatsby,ChristopherBiscardi/gatsby,mingaldrichgan/gatsby,gatsbyjs/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,0x80/gatsby,gatsbyjs/gatsby