Decouple Coreclr Test and Product build

[jashook]

Currently our test build requires build.cmd/sh to complete. This is a bottleneck for our CI, without it our long poles are serialized on each other.

In order to accomplish this the test build will need to split apart the managed test build from the native test build. The native test build will happen as a separate step, that can be run right after the product build.

Note this is a larger issue tracking the end goal. The work items required to reach it are below.

Related to

• Execute x64 CoreCLR tests dlls on arm32 #31793
• Change coreclr YML to build tests and product in parallel #33067

Work items

1. Added OS and Bit Specific tags to accordingly .csproj files. #637
2. Coreclr - Add the ability to include or exclude test metadata during test build time #33072
3. Change the coreclr managed test build to build platform/arch specific tests separately #34507
4. [CI] Hoist the platform/arch independent test build into its own job #34508

[marek-safar]

Please also think about producing test artefacts which can be used by multiple runtimes instead of building it for each runtime

[sdmaclea]

This is complete at least in dev\infra