eolian-mono: Add support for partial classes

eolian-mono: Add support for partial classes

Summary:
Add the -p command to eolian to create a class as a partial
class. Create a list in meson build of Eolian files that should be
built with partial classes.

This allows creating more specific method overloads for C#, manually,
by generating the class as partial and adding in manual binding the
partial class with the new methods and properties.

T8034

Reviewers: segfaultxavi, lauromoura, woohyun, Jaehyun_Cho

Reviewed By: lauromoura

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9690