llvm/test/TableGen/intrinsic-*.td: Use Intrinsics.td instead of mock

- `intrinsic-pointer-to-any.td`
- `intrinsic-varargs.td`

They used their own mock.

I have introduced `TEST_INTRINSICS_SUPPRESS_DEFS` in `Intrinsics.td`.
Tests of intrinsics may use it.

Differential Revision: https://reviews.llvm.org/D146147