Fine. Add tests for static getters, setters, methods.

And also some instance member tests.

And constructors for type extensions.
But these are missing the primary constructor.
I will look why and fix in a future CL.

Change-Id: I882bd9725cce9976fd878eeac13d03a0306f58a1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/444204
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov