[Ide] Add new PlatformService.OpenTerminal variant

It supports setting the window title and environment variables.
[Core] Add explanatory comment for a hack
[Windows] Implement PlatformService.OpenTerminal
[MSBuild] Builder interface library doesn't need to be an x86 exe

Make it an AnyCPU library to fix warnings and prevent executing it.

Assembly identity is still the same.
[MSBuild] Add assembly redirects to v12 builder
[MSBuild] Reorganize the builders' assembly redirects