JS backend: fix KT-6037 (default arguments in simple function with expression as body)

#KT-6037 Fixed
Check that boxing instruction is simple call

like T.valueOf(unboxType(T))

 #KT-6047 fixed
Add tests for obsolete "nested class is inaccessible"

 #KT-3535 Obsolete
 #KT-3647 Obsolete
 #KT-3731 Obsolete
Delete unused JavaSignatureFormatter
Fix Double and Float equality/hashCode in data classes

 #KT-5818 Fixed
Generate lambdas in enum entry super calls

 #KT-4423 Fixed
Prohibit to override equals/hashCode in enums

 #KT-5721 Fixed
Make enum classes comparable

 #KT-3727 Fixed
Prohibit all modifiers for enum entries

 #KT-2679 Fixed
Regenerate .txt test data on enums

Now they have final equals, hashCode and compareTo
Minor, fix some warnings in DeclarationsChecker
Make 'when' on nullable enums exhaustive if 'null' entry is present

 #KT-2902 Fixed