Stop ngening compat-only DLLs in subfolders

[rainersigwald]

These DLLs are shipped to these subfolders only for compat with applications that load from them naïvely; MSBuild.exe and VS and applications that use MSBuildLocator should only ever load them from the bin\ directory directly. So stop spending time ngening them.

Notes to January self: look at ngen logs in VS perf tests. Verify

• no methodsJitted regressions
• we are actually not ngening these files for x86 or amd64

[dotnet-policy-service]

Hello @rainersigwald, I noticed that you’re changing an .swr file or any file under src/Package/MSBuild.VSSetup.. Please make sure to validate this change by an experimental VS insertion. This is accomplished by pushing to an exp/* branch, which requires write permissions to this repo.

[rainersigwald]

Experimental insertion results on this one are weirder: https://dev.azure.com/devdiv/DevDiv/_git/VS/pullrequest/599728.

Specifically there seems to be a consistent regression that Common7\IDE\PublicAssemblies\Microsoft.IO.Redist.dll is in VM_AdjustedImagesInMemory_Total_devenv in a few scenarios where it wasn't before. But why?

filtering that metric with "show identical" shows that in both cases it's loading C_\Windows\assembly\NativeImages_64_HASH_\Microsoft.IO.Redist.ni.dll, so it sure looks like it's still getting ngened by whatever puts it in PublicAssemblies . . .

And looking at the ngen64 logs (baseline on the bottom):

❯ rg 'install ".*Microsoft\.IO\.Redist\.dll\"'
ec07b127fa38ea2503e95b117bca1117\TestExecutionOutputs\ManagedLangsVS64.AddNewProject\Warmup-1-20250109-215559_dtl-bienvy1e\NGenLogs\Framework64\ngen.log
1412:01/09/2025 21:07:23.011 [8236]: Executing command from offline queue: install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:1
1423:01/09/2025 21:07:23.065 [8236]: Executing command from offline queue: install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\MSBuild\Current\Bin\MSBuild.exe" /queue:1
1857:01/09/2025 21:07:24.059 [8236]: Executing command from offline queue: install "C:\VisualStudio\Common7\IDE\PublicAssemblies\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:3

ccaff841d82a52d8d1308341cd65e0a7\TestExecutionOutputs\ManagedLangsVS64.AddNewProject\Warmup-1-20250109-052236_dtl-juijkiyh\NGenLogs\Framework64\ngen.log
1536:01/09/2025 04:35:42.045 [3496]: Executing command from offline queue: install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:1
1593:01/09/2025 04:35:42.303 [3496]: Executing command from offline queue: install "C:\VisualStudio\MSBuild\Current\Bin\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\MSBuild\Current\Bin\MSBuild.exe" /queue:1
1761:01/09/2025 04:35:42.714 [3496]: Executing command from offline queue: install "C:\VisualStudio\MSBuild\Current\Bin\amd64\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:3
1855:01/09/2025 04:35:42.867 [3496]: Executing command from offline queue: install "C:\VisualStudio\Common7\IDE\PublicAssemblies\Microsoft.IO.Redist.dll" /NoDependencies /ExeConfig:"C:\VisualStudio\Common7\IDE\vsn.exe" /queue:3

So . . . it's redundantly ngened still.

[rainersigwald]

Remaining redundancy from that log addressed by #11256.