* 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