* Reject requests for hot reload if a hot reload is already in progress.
Fixes#14184
* Implement TODO, verifying further hot reloads complete sucessfully.
* Fix year on new file.
* Add missing type annotations to fix lints
* Add run_machine_concurrent_hot_reload to manifest for CI
* Reformat document
... but undo things that cause lints (like single-line ifs)
* Extract std stream transformations
* Make inProgressHotReload private
* Disallow all types of reload while hot reload in progress
* Simplify code handling in-progress hot reloads
