Check static private methods on super class are called with correct receiver

[mkubilayk]

Adds coverage for (static) private methods according to the test plan posted in #1343.

Semantics > Error on missing method

• Subclass receiver for static private

@leobalter @rwaldron for review.
cc: @caiolima @jbhoosreddy

[caiolima]

LGTM.

It would be awesome see some tests covering cases where private static method is used on inner class, functions and Arrow functions. I would recommend do this in this PR, but it is up to you if you want separate them.

[leobalter]

found one nit. The features flags are being used by some consumers of Test262, it's nice to have them properly.