Group dumped declaration by declaration kind (class, function, property, etc.)

[fzhinkin]

Currently, all dumped declarations are sorted lexicographically, potentially by mixing different kinds of declarations. That approach differs from what we do for JVM dumps, where declarations are grouped by a declaration kind.

With this change, declarations will be ordered as follows:

• Firstly, by how common are they w.r.t. set of targets: more common declarations will be printed first, followed by less common ones;
• If two declarations share the same set of targets, they will be compared by their kind (class, function, property, etc.): depending on the context (top-level declaration vs nested), the order will be chosen using rules listed below;
• Finally, if two declarations share the same target sets and are of the same kind, we'll compare them lexicographically.

This PR introduces the following order:

• For top-level declarations:
  • annotation
  • enum class
  • interface
  • regular class
  • object
  • const val
  • val
  • var
  • functions
  • everything else
• For nested declarations:
  • constructor
  • enum entry
  • const val
  • val
  • var
  • function
  • annotation
  • enum class
  • interface
  • regular class
  • object

Closes #197

[ilya-g]

I have a feeling that the sorting test doesn't specifically test sorting inside groups. For example, try replacing lhs.text.compareTo(rhs.text) with 0 and see if there will be failures to sort declarations inside groups.

[fzhinkin]

@ilya-g using a fixed value instead of lhs.text.compareTo(rhs.text) leads to test failures (both unit- and functional-tests).

But I agree that a test explicitly covering ordering is missing, I'll add it.