Improve SDK build performance

CI builds
- Loc build takes 10 minutes longer than the longest windows leg. We should consider moving this to a separate pipeline that runs daily
- We build a bunch of test packages that used to be used in the installer repo but aren't needed anymore since we don't test there (unless we use these for the VMR eventually). Anything testSdk*.
- SignToolTask takes 19 minutes to run
- There are a bunch of items under the NonShipping folder being signed. Some of them problem should be but many of them shouldn't (keep signing the VS.Redist packages for example)
- is there a reason we're building or signing dotnet-toolset-langpack?
- same question for dotnet-toolset-internal?
- There are about a dozen double writes to get rid of though probably won't save much time

Dev Builds
- Most of the time is in CoreCompile for me (4min)
- CoreGenerateSatelliteAssemblies is 27 seconds
- 40s in copy we should look into

PR builds

PR test runs
- Tests per helix work item should be explored