* If `toArray` is inherited from Java, it may take an argument or
return a value of a flexible type, which looks nullable in IR;
* The returned array may also have `out` variance of the type
argument;
* `Array<T>` is not the same as `Array<Any?>` if `T` is neither `Any`
nor `in Something`, so presence of `toArray(): Array<T>` does not
mean we don't need to generate a new `toArray`.
Library methods such as 'listOf' are resolved
to have the package fragments as their parents,
but JVM expects their containing file classes as parents.
This fix generates those file classes and
uses them as parent replacements for such library methods.
This allows us to not generate redundant immutable collection
stubs. The code to generate the immutable collection stubs does
not deal well with thinking that all external declarations
come from Java.
[JS IR BE] Runtime fixes
* Do not generate external declarations for IR BE
* Move `arrayToString` helper function out of shared JS stdlib
* Fix arrays type check for IR BE
Mikhail Glukhikh