Run `test-prove-functional` as part of `performance-test-kevm.sh`

[geo2a]

The KEVM CI is currently failing on a K update in the Proofs: functional job. It is unclear at that point if the backend is the cause of this. In any case, I've noticed we are not running the functional specs from the KEVM test suite when measuring performance, as we only run the test-prove-rules Makefile target. We should run test-prove-functional as well, perhaps in a separate invocation so that the normal tests and the functional ones do not run concurrently.