Fix mbedtls_pk_copy_from_psa() and mbedtls_pk_copy_public_from_psa() to
still work when the algorithm in the key policy is not an RSA
algorithm (typically PSA_ALG_NONE). Add a dedicated test case and adjust the
test code. Fixes the test case "Copy from PSA: non-exportable -> public, RSA"
when MBEDTLS_PKCS1_V15 is disabled.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>