Pickling for morphisms of modules with basis defined by a matrix

[nthiery]

The class
sage.modules.module_with_basis_morphism.ModuleMorphismFromMatrix
and TriangularModuleMorphism with inverse_on_support="compute"
do not pickle properly. See the comments and examples near their
respective TestSuite test.

A first potential route would be to use pickling by construction for
those classes. Another one -- more general -- would be to implement
pickling for methods of dictionaries / builtin types:

sage: d = {1:2}
sage: dumps(d.__getitem__)
...
TypeError: expected string or Unicode object, NoneType found

sage: dumps(dict.__getitem__)
...
PicklingError: Can't pickle <type 'method_descriptor'>: attribute lookup __builtin__.method_descriptor failed

This is a follow up to #8678.

Component: pickling

Issue created by migration from https://trac.sagemath.org/ticket/17957