chore(doclint): support classes inheritance (#935)

This patch:
- gives meaningful names to doclint tests
- supports classes inheritance in documentation linter. When class A
  extends class B, all methods of class B are added to documentation of
  class A.

This is a prerequisite for Object Handles: ElementHandle will be
extending ObjectHandle.

References #382

utils/doclint/check_public_api/test/diff-arguments/result.txt

@@ -0,0 +1,4 @@
+[MarkDown] Heading arguments for "foo.test(...files)" do not match described ones, i.e. "...files" != "...filePaths"
+[MarkDown] Method Foo.constructor() fails to describe its parameters:
+- Argument not found: arg3
+- Non-existing argument found: arg2