MatrixObj: Add type-parametrized tests

[ssiccha]

Add test functions which take as argument something like IsGF2MatrixRep (to indicate a specific MatrixObj implementation) plus some other arguments (e.g. a base domain) and then run a bunch of tests to verify that certain APIs are implemented right. E.g. a ZeroMatrix test could ensure that matrices of the right dimension, domain and type are produced.

The file tst/teststandard/arithlst.g might give an idea how such generic tests can look.

Then we can:

• run these against existing and new implementations
• fix all issues uncovered this way (by adjusting the implementation, the
  documentation, the tests or several of the above)
• also add specialized tests for implementations which complement the
  generic ones.

[fingolfin]

Also take a look at tst/testinstall/MatrixObj/testmatobj.g

[fingolfin]

@AnnaKDS and @wucas are working on this as part of GAP Days Summer 2022