Prebuilt report should indicate which TFMs are being used

As part of the effort to [eliminate building net4* TFMs](https://github.com/dotnet/source-build/issues/3014) in source build as well as the work to improve the SBRP tooling, it has been realized that SBRP contains a lot more TFMs than strictly necessary. This is undesirable for the following reasons:

1. Increases the build time
2. Requires additional targeting packs. Targeting packs are required to build these SBRP to prevent prebuilts. The conjecture is there are some targeting packs that exist just for the purpose of building SBRP.
3. Increases the size of the repo (large)

The primary reason for this is that when an SBRP is needed, the generate tooling is run which generates the ref packs for a fairly broad subset of TFMs. Only a small subset of TFMs have been filtered out in the past.

Only the required minimum set of TFMs should be generated. To support this, the prebuilt reports should be updated to indicate which TFMs are being referenced from the prebuilts. These TFMs can then then be specified to the SBRP tooling as the set to generate (passing in a set of TFMs to generate is already supported).