Move Foundation unit tests into own folder

move our tests (e.g. VM/merkle/state) into a separate folder and make ourselves owners of that folder

remove ourselves from the list of owners of other tests (such as generic platform/consensus-specific tests)

Start by locating the Foundation tests mentioned in the issue, including VM, merkle, and state tests, and identify the ownership configuration for those and the generic platform or consensus-specific tests. Move the Foundation tests into their own folder, make the Foundation team owners there, and remove their ownership from the other test areas. Run the relevant unit tests to confirm they still pass.

Written by the indexing model from the issue text.