Move webui protos to SteamKit2.WebUI.Internal

[xPaw]

Also added a few new ones. They are useful to have, but the way webui dumping works, I'm not confident in it long term.

I did not generate webui/common, because that ends up being a 1mb file, and we can reuse Steam common protos.

Dumper code lives here: https://github.com/SteamDatabase/SteamTracking/blob/master/dump_javascript_protobufs.mjs

[JustArchi]

Could you consider adding https://github.com/SteamDatabase/Protobufs/blob/master/webui/service_familygroups.proto too? Would help me over in ASF, thank you in advance 🙏

[xPaw]

Family groups exist in Steam protos, so generated here: 530f8e4

[JustArchi]

Great, thanks a lot! 👍

[ezhevita]

Please consider adding service_loyaltyrewards.proto (used by ASF) and service_accountcart.proto with service_checkout.proto for generation

[xPaw]

The annoying thing about cart and checkout protos is that they actually require webui/common, but the generator does not really support only generating the messages that are used. I don't want to bring 1mb of common protos in steamkit.

If the generator somehow could just copy stuff it needs from common, that would solve this issue.

[xPaw]

After some discussion, as these protos are useful to have, and trying to solve common protos is a bit of a pain, i'm gonna include them.

This should be solved by fixing trimming instead: #1057