Improve testData generator for reserved words.

Cashing iterator in CyclicStream.
Detect generating unexpected testdata file(e.g. may caused because of bug in stdlib).
Regenerate testData for reservedWords after take was fixed.
JS backend minor: added @NotNull annotation to getArguments()
KT-4773: added tests
KT-4773: use receiver for delegated extension property
KT-5673: added tests
KT-5673: always write val property to backing field
More changes after replacing config directory

 - Plugin auto-enable script updated
 - Don't drop configured folder in update-dependencies
 - Drop test config and system folders in update-dependencies
KT-5873 Exception in ArgumentMatchImpl on smart completion
 #KT-5873 Fixed
Rename: this object, receiver argument -> dispatch receiver, extension receiver
Rename: auto cast -> smart cast