chore(config): Migrating `ENABLE_JAVASCRIPT_CONTROLS` from app config to a feature flag (#19113)

* first pass migrating config to ff

* nixing a console log from testing

* adding an entry to `UPDATING.md`

* linting :sparkles:

* Adding ENABLE_JAVASCRIPT_CONTROLS to FEATURE_FLAGS.md

* no longer in need of state!

* Turning the flag back off

* linting... le sigh

* and more linting...