Project System: VSHost replacement

[davkean]

Currently csproj/msvbproj uses vshost.exe to "speed up" F5 debugging for desktop client apps.It is also used for immediate window evaluation without starting a debugging session. We need to figure out if we are going to bring this forward to CPS or not.

[davkean]

ClickOnce partial trust support is also handled by VSHost.

[tmat]

@tmat

[KirillOsenkov]

Note that using VSHost prevents you from inspecting most optimized variables in Watch/Locals/etc. windows. I always turn it off (and enable COMPLUS_ZapDisable=1) to actually see the variables in the debugger. My understanding is that the vshost process doesn't inherit environment from devenv, so COMPLUS_ZapDisable=1 has no effect.

I've never seen any benefit from VSHost being turned on. No perceptible perf improvement at all.

[davkean]

This issue was moved to dotnet/project-system#66