NGEN all System dependencies with ngenApplications=MSBuild.exe (#6666)
NGEN all System dependencies with ngenApplications=MSBuild.exe (#6666)

Fixes #6605 

### Context

MSBuild.exe is being JITted because NGEN images of some of its dependencies are rejected.

### Changes Made

Use `vs.file.ngenApplications="[installDir]\MSBuild\Current\Bin\MSBuild.exe"` for all system dependencies to pick up our binding redirects.

### Testing

- Experimental insertion confirmed that MSBuild.exe is no longer JITted (both x86 and x64). On x64 the number of methods compiled when building a simple hello world app went down from 1862 to 1536, time spent in JIT 810 ms -> 608 ms.
- No RPS regressions.
sean-gilliam/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild