Update protobufs

[xPaw]

1. Skipped Underlords protos because it requires some generation changes.
2. Removed EnumeratePublishedFiles because all the protos for it are gone; can't obsolete it because CMsgCREEnumeratePublishedFilesResponse was removed and it won't compile.
3. Combined SteamKit2.Unified.Internal to SteamKit2.Internal because some protos depend on each other and they're in separate namespaces.
   If this change is not acceptable, then protobuf generation needs to be upgraded to allow adding usings.

[codecov]

Codecov Report

Merging #827 into master will increase coverage by 0.13%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #827      +/-   ##
==========================================
+ Coverage   22.75%   22.89%   +0.13%     
==========================================
  Files          95       95              
  Lines        9344     9283      -61     
  Branches      780      779       -1     
==========================================
- Hits         2126     2125       -1     
+ Misses       7084     7024      -60     
  Partials      134      134              

Impacted Files	Coverage Δ
...SteamKit2/Steam/Handlers/SteamFriends/Callbacks.cs	0.00% <ø> (ø)
...dlers/SteamUnifiedMessages/SteamUnifiedMessages.cs	7.76% <0.00%> (ø)
...t2/SteamKit2/Steam/Handlers/SteamUser/Callbacks.cs	2.77% <ø> (ø)
...teamKit2/Steam/Handlers/SteamWorkshop/Callbacks.cs	0.00% <ø> (ø)
...Kit2/Steam/Handlers/SteamWorkshop/SteamWorkshop.cs	12.32% <ø> (+2.98%)	⬆️

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[yaakov-h]

I think this makes sense, but wouldn't mind a second opinion.

What changes need to be made for Underlords?

[xPaw]

What changes need to be made for Underlords?

Needs to bring in a bunch of more proto files like user messages, can't be bothered to deal with it.

[voided]

I think this makes sense, but wouldn't mind a second opinion.

Most of this looks good to me as well - I think I originally suggested merging the internal namespaces on IRC. They're internal anywhere so the implication is that breakage here from time to time is expected.

I could go either way on EnumeratePublishedFiles - should it be an Obsolete stub that does a no-op, should it throw an exception, or should it be removed entirely? All three approaches seem fine.

[yaakov-h]

An obsolete stub could just cause consumers to leak resources, waiting for an event that never fires.

Throwing an exception sounds good, but removing the method will also cause an exception to be thrown... just far more cryptically.

I think all-up I'd rather keep the method, make it throw an exception, mark as obsolete and optionally hide it with EditorBrowsableAttribute.

[xPaw]

Anything blocking this? There are proto updates that I'd like to use.