JS lib: simplify DefaultPrimitiveHashSet.
JS lib: provide Kotlin object as parameter of IIFE.
Minor: added regression tests for KT-4235

#KT-4235 Obsolete
Minor: added regression tests for downTo.

Adopted tests from patch attached to KT-2586.
Update to EAP 139.144.2
Added regression tests for KT-3518 Null pointer during null comparison in JS Backend.
Added regression tests for KT-1906 Support invoke() convention is js-backend (including classes implementing Function trait)

#KT-1906 Fixed
Added regression tests for KT-2474 Range lacks reverse() in JavaScript backend

#KT-2474 Fixed
Correct Android variant compile task name

Corrects 'compiledebugKotlin' to 'compileDebugKotlin'
Support creating flexible types in tests

Flexible types can not be created in normal user code, but if there's a special classifier `kotlin.internal.flexible.ft` with two type parameters,
its occurrences are replaced by flexible types, e.g. `ft<Int, Int?>` becomes `Int!`
Removing the static import that caused exception on compilation
CHECK_TYPES injected through imports
DescriptorRenderer can now render flexible types for code (i.e. `ft<L, U>`)
toString() for easier debugging
Clean up declarations of runReadAction() etc
KT-6059 Regression: irrelevant compiler error on trait inheritance (worked in M8)

 #KT-6059 Fixed
KT-6077 Compiler does not issue error on unsafe access to ArrayList with nullable values

  #KT-6077 Fixed
Compilation errors fixed
Generation of ++ and += fixed for platform types
Merge pull request #521 from ronshapiro/patch-1

Correct Android variant compile task name