Implement basic C# translation parser plugin

[leNicDev]

This PR implements a basic C# translation parser plugin. It extracts Tr, TrN, Atr and AtrN calls from C# scripts and generates entries for the POT file generator. The implementation is very basic compared to the GDScript translation parser because we can't properly parse C# source code for obvious reasons.

I have no prior C++ experience at all. I only implemented this because I needed it for my project.

[Starkium]

this is neat, we're currently not working in master at the moment. We'll have to come back and look at this after we got all the rebranding stuff done and into master.

[scgm0]

Is it possible to write this feature in C#? Just like the C# export feature, if write this feature in C#, should have an advantage in parsing the C# source code.

[Spartan322]

I would also like to see this type of feature sent upstream to Godot, though yeah probably a better plan if this could be done from C# for source code parsing reasons.

[SkogiB]

Since we've re-assessed our position on sending things upstream by default recently, we can take a look at this closely soon

[Spartan322]

Changes to this PR were already requested, the author has not come back.

[molingyu]

I think this function should be implemented by Godot.NET.SDK. Obviously, using C# can use the ast parsing tool provided by Roslyn to better obtain the parts that need to be generated. This is more accurate than the current implementation.

[molingyu]

godotengine/godot#99195

I finished it