[K2] Support generating documentation for stdlib

[vmishenev]

Currently, it is blocked by #3137 and (possible) https://youtrack.jetbrains.com/issue/KT-56076/K2-build-Kotlin-standard-library

StdLib is a specific Kotlin library that can require supporting extra flags to analyse and build the documentation. For example, in Dokka K1 the flag ignoreCommonBuiltIns should be enabled to analyse stdlib.

Dokka K2 should have the possibility to generate correct documentation for stdlib.
The result documentation should have no difference from the output generated by Dokka K1.

Technical details

It can require enabling AnalysisFlags.allowKotlinPackage in the Analysis API. Also, extra analysis flags can be needed.

[whyoleg]

First tests which are specific to stdlib and are failing now for K2 are added in #3349 to ObviousAndInheritedFunctionsDocumentableFilterTest (in the end of file). They are now muted with OnlyDescriptors until this issue is resolved

[IgnatBeresnev]

Need to keep an eye on the issue and how it's resolved for compiling K2, and go from there.

[vmishenev]

Requires #3939