Steam2.dll support needed for multiple games

Feature Request

I confirm:

• that I haven't found another request for this feature. There are multiple requests, but they are scattered over the issue tracker.
• that I have checked whether there are updates for my system available that
  contain this feature already.

Description

Do what's needed to get the Steam2.dll file working, so that more games can run. I'm not sure if the file is missing or corrupt or something else.

Justification

I've collected all issues related to the Steam2.dll problem, so that the Proton developers have a central place to find and track this issue.

I think problems with files named Steam2.dll something should probably be fixed in Valve's Proton? So that would be the reason to integrate into Proton, instead of Wine.

Risks

• Licensing issues.
• Fix for file might break something else.

Affected games

#265
#392
#420
#651
#2280
#2361
#2454
#2609
#2633
#2649
#2650
#2652
#2655
#2679
#2685

False alarms, no steam2.dll found in log:

#567

Seems this is fixed now somehow:

https://github.com/ValveSoftware/Proton/issues/2645#issuecomment-522311580

Seem this one is fixed too using proton 4.11.2

#2672

PinballFx 3 gives a new error now:

#346 Proton 4.11-8 : Steam2.dll error is not present anymore but game still crashes. The error is now gameserver.cpp (682) : Assertion Failed: usGamePort != usQueryPort
https://github.com/ValveSoftware/Proton/issues/346#issuecomment-555268574

Review the linked affected-game issues and the Proton/Wine handling of Steam2.dll; no source file, test, or entry point is identified. Determine whether the DLL is missing, corrupt, or requires an implementation, then validate that affected games no longer report the error without regressions.