Add jit test project checker as jit test (dotnet/coreclr#9721)

Add jit test project checker as jit test (dotnet/coreclr#9721)

Add the tool used to fix/repair projects as a test case. It will
fail with an error code if any project file in the jit test subtree
needs fixing.

This test requires CORE_ROOT to point at the test overlay and
that directory be rooted under the repo (other test cases already
have similar requirements).

CodeGenBringUp tests are noted as needing fixes, but are accounted
for under the category of "deferred fixes".

Commit migrated from https://github.com/dotnet/coreclr/commit/cdea3db0927e279c6d9bd6531bff84e4cbd94eaa