perl-functions.eclass: add perl_get_module_version

perl-functions.eclass: add perl_get_module_version

This utility provides informational data describing the given module
names state of installation, either as a version, or as an error
message describing the grade of failure incurred in module loading.

It has the side effect that it most load the module (and its
dependencies) into memory to give a report value, and can be expensive
and have side-effects from Perl code execuring while the module loads,
including (but not limited to) people calling POSIX::_exit

This is the slowest way of inspecting state about a module, as
it must load the module