* Revert "Convert Extension to a string enum (#16425)"

This reverts commit 09321b3.

* Revert "Also convert ClassificationTypeNames and CommandTypes/CommandNames"

This reverts commit f94818d.

* Revert "Make ScriptElementKind and HighlightSpanKind string enums"

This reverts commit b162097.

* Revert "Make ScriptElementKind and HighlightSpanKind string enums"

This reverts commit b162097.

# Conflicts:
#	lib/lib.d.ts
#	lib/lib.es2016.full.d.ts
#	lib/lib.es2017.full.d.ts
#	lib/lib.es5.d.ts
#	lib/lib.es6.d.ts
#	lib/lib.esnext.full.d.ts
#	lib/tsc.js
#	lib/tsserver.js
#	lib/tsserverlibrary.d.ts
#	lib/tsserverlibrary.js
#	lib/typescript.d.ts
#	lib/typescript.js
#	lib/typescriptServices.d.ts
#	lib/typescriptServices.js
#	lib/typingsInstaller.js

* Update LKG

* Revert "Make CommandTypes a const enum and use `allCommandTypes` for unit test"

This reverts commit f6240cb.