Use protobufs from submodule

[psychonic]

As discussed from time to time, use SteamDB's Protobufs submodule instead of continuing to maintain our own. This makes keeping up to date simpler.

Using
https://github.com/SteamDatabase/Protobufs

Since we can't have individual generate scripts for each app in the folder with their proto files, instead switched to single script to regenerate all, running from the Protogen folder. If that's not desired, we can still do individual bats, just ran from elsewhere. This just removed much of the boilerplate needed.

Also, with this change, the classes for the new Steam chat are using the protos from Steam Client itself, rather than from the friends js.

[xPaw]

I suggest removing gc.proto and using the proto from steam/steammessages_base.proto instead.

That has all the new fields, except for 200/201 which I suspect are only sent between GC servers anyway.

[voided]

Can we take CS:GO's GC protobuf header for our gc.proto?

They've got an extra ip field which you wouldn't be able to get at otherwise.

Ideally sometime in the future we can maybe make the headers pluggable depending on what GC you're talking to - and this would become even more important if they ever diverge (hasn't happened so far...).

[voided]

Just needs another regen, but this looks good to me.

[yaakov-h]

Note to self: close #16 on merge.

[yaakov-h]

Neat!

[yaakov-h]

Probably something for a later stage, but I'd love to have this automatically submit a PR when the protobufs repo gets updated.

[yaakov-h]

Build error is in NHA2:

Specializations\TF2\TF2SOHelper.cs(21,27): error CS0246: The type or namespace name 'CSOPartyInvite' could not be found (are you missing a using directive or an assembly reference?)

[xPaw]

@yaakov-h That proto only exists in CS:GO now: https://github.com/SteamDatabase/Protobufs/search?q=CSOPartyInvite&unscoped_q=CSOPartyInvite

It was generated from tf2 beta before.

[codecov-io]

Codecov Report

Merging #610 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #610      +/-   ##
==========================================
- Coverage   23.63%   23.61%   -0.03%     
==========================================
  Files          85       85              
  Lines        8694     8694              
  Branches      719      719              
==========================================
- Hits         2055     2053       -2     
  Misses       6508     6508              
- Partials      131      133       +2

Impacted Files	Coverage Δ
SteamKit2/SteamKit2/Steam/WebAPI/WebAPI.cs	41.34% <0%> (-0.49%)	⬇️
SteamKit2/SteamKit2/Types/SteamID.cs	79.42% <0%> (-0.37%)	⬇️

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