Review/Fix MSBuild ngen registrations

[JanKrivanek]

Context

Reported by @davkean:

Its super unclear why all MSBuild binaries in general are being registered for all architectures too (we only should register 32-bit for 32-bit and 64-bit for 64-bit), those 32-bit vsn.exe are definitely wrong as we don’t ship a 32-bit version of VS, so we’re wasting end-user machine resources.

Goal

Only required registrations are issued

[YuliiaKovalova]

Sub-issue
#10847

[rainersigwald]

Looking at this as part of #11145, and I think we need Setup features or a pretty big package refactor to do it right.

Specifically, we want our core assemblies and their transitive closure to be ngened in several contexts:

Context	controlling config	arch	file
VS in-proc	vsn.exe	amd64 or arm64	bin\Microsoft.Build*.dll closure
Mainline CLI	bin\amd64\MSBuild.exe	amd64	bin\amd64\MSBuild.exe bin\Microsoft.Build*.dll closure
Old CLI and 32-bit taskhost	bin\MSBuild.exe	x86	bin\MSBuild.exe bin\Microsoft.Build*.dll closure
arm64 CLI	bin\arm64\MSBuild.exe	arm64	bin\arm64\MSBuild.exe bin\Microsoft.Build*.dll closure

But I don't see a way to express in the .swr or the VSIX manifest things like "ngen bin\Microsoft.Build.dll for amd64 with bin\amd64\MSBuild.exe.config and vsn.config and also for x86 with bin\MSBuild.exe.config".

Today, we run:

[framework]
install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.Build.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\MSBuild\Current\Bin\MSBuild.exe" /queue:1
install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.Build.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:1

[framework64]
install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.Build.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:1
install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.Build.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\MSBuild\Current\Bin\MSBuild.exe" /queue:1

• the 32-bit vsn.exe one is unnecessary
• 32-bit msbuild.exe is important for CI
• 64-bit vsn.exe is critical
• 64-bit msbuild.exe is critical (but is it getting the right context here? At runtime it'll get bin\amd64\MSBuild.exe.config but it's running with just bin\MSBuild.exe.config)

[JanProvaznik]

reverted #11182 which contributed to this:

Regresses VM_AdjustedImagesInMemory_Total_devenv e.g. here:
https://devdiv.visualstudio.com/DevDiv/_git/VS/pullrequest/606301