Automatically generate properties for packet fields

[TSRBerry]

This PR adds a source generator to generate property implementations for packet fields.

C# 13 (.NET 9.0) adds support for partial properties and source generators are able to provide implementations for them.
This generator looks for the new PacketField attribute which can be applied to properties and generates the appropriate implementation based on the provided arguments and the property type.

It handles every packet field that's currently implemented by RyuSOCKS.

The generator currently supports the following features:

• Constant and dynamic offsets for packet fields
• Constant and dynamic lengths for packet fields
• Little and big endian support for packet fields
• Generation for the following property types:
  • simple numeric types (byte, sbyte, ushort, short, ushort, int, uint, long, ulong)
  • enums
  • strings
  • arrays of enums and simple numeric types
  • System.Net.IPAddress
• Min/Max length checks for arrays and strings
• Invocation of custom validation methods before executing the setter/getter functions

---

There are a few things that I want to do before this gets merged:

• Add tests
• Check other projects like https://github.com/dotpcap/packetnet and figure out if it makes sense to turn this generator into a standalone NuGet package
• Fix all the FIXME comments
• Create issues for all TODO comments
• Consider implementing AddVerificationMethodIfNecessary() in a different way to make it less awkward to use
• Restructure the helper properties and methods of the RyuSOCKS packets

[AnonymusNW]

Made some comments about possible improvements.
Also why are there multiple classes just called "TestPacket" or similiar?
In e.g.: RyuSocks.Generator.Test/data/PacketGenerator/Namespaces/TestPacket.cs

[TSRBerry]

Made some comments about possible improvements. Also why are there multiple classes just called "TestPacket" or similiar? In e.g.: RyuSocks.Generator.Test/data/PacketGenerator/Namespaces/TestPacket.cs

Thank you very much! I'll address your comments shortly.

All the files in RyuSocks.Generator.Test/data are used by PacketGeneratorTests.GeneratedSources_AsExpected(). It reads the source file, runs the generator and compares the results to the expected generated files (and also checks for compilation errors).
I recently learned that this seems to be called snapshot testing?

[AnonymusNW]

lgtm

[TSRBerry]

With the latest commits, all FIXME comments have been fixed!

We now support all string encodings which are exposed by System.Text.Encoding.
.NET Core also exposes Latin1 encoding, which is not supported, since we currently aren't able to test it properly.

The test coverage for the new encoding code is ~99%, the uncovered code is about exceptions, which I plan to add tests for soon.
And with that we also achieved ~99% test coverage of AccessorGenerator.Simple.cs!

[AnonymusNW]

two remarks, else lgtm