fix: enable transform-block-scoping with generators feature (#12806)

[IlyaSemenov]

Q	A
Fixed Issues?	Workaround for #12806
Patch: Bug Fix?	👍
Major: Breaking Change?	-
Minor: New Feature?	-
Tests Added + Pass?	👍
Documentation PR Link	-
Any Dependency Changes?	-
License	MIT

This adds generators to transform-block-scoping features:

babel/packages/babel-compat-data/scripts/data/plugin-features.js

Lines 104 to 106 in 2942629

	"transform-block-scoping": {
	features: ["const", "let"],
	},

as asked by @nicolo-ribaudo in #12806, and adds a regression test for Chrome 49 preset.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/54379/

[IlyaSemenov]

I am not sure why the tests wouldn't pass. It's like it's ignoring the new compat-data. 🤷

[JLHwung]

Can you also update packages/babel-compat-data/data/plugin-bugfixes.json? I believe that is why CI is failing.

[IlyaSemenov]

Updated. It passes all tests locally with make test-only and yarn jest --ci, but still fails some CI checks.

[nicolo-ribaudo]

I updated the Babel 8 tests, hopefully CI will be green now :)