Support partial classes

[handzlikchris]

Partial classes need to be correctly rewritten.

Possibly best approach is to pull all partial classes files into single and compile.

[ ] reach back to tommox86 from forum thread

[RunninglVlan]

Just wanted to mention that I am noticing more and more partial class usage for generating some boilerplate code using source generators - latest Unity UITK, Unity ECS, Lombok.NET

[RunninglVlan]

Found another issue with partial classes. When combining them, we need to order the class's base types correctly: the parent class should come first, followed by interfaces.