Drop Support for Unity 2023.2

[rblenkinsopp]

Unity no longer supports Unity 2023.2 and there are now 2 LTS versions that are currently in support (6.0 and 6.3).

We should consider dropping 2023.2 and removing dead code pathways. This possibly could consitute requiring a major release.

[MaxPalmer-UH]

Yes, that makes for a lot of sense - moving to 6 would be a significant shift. We could should also consider making URP materials and shaders the default and then allow people to downgrade or even drop support for BiRP. Any thoughts from anyone else?

[MaxPalmer-UH]

We should also do something about the fact that the service might be listening on different ports, depending on the installed version. Currently, I? find myself having to remember to change the port number depending on what I've got installed/am testing.

[rblenkinsopp]

I want to rework this a bit on my new LeapC branch as well as from looking at the code some options (server-namespaces) are just not supported in the newer versions so I'd rather just surface the IP/Port options.

We could make the change to support the two default ports there as well.