Don't generate test cases for ALG_FFDH without KEY_TYPE_DH

[gilles-peskine-arm]

generate_psa_tests.py generates some test cases that depend on PSA_WANT_ALG_FFDH disabled but PSA_WANT_KEY_TYPE_DH_KEY_PAIR_BASIC enabled. This is a silly configuration that we don't test.

Goals of this task (modeled on Mbed-TLS/mbedtls#9573):

• Don't generate such test cases.
• Remove the exception from analyze_outcomes.py
• Ensure that crypto_adjust_*.h auto-enables PSA_WANT_ALG_FFDH and PSA_WANT_KEY_TYPE_DH_KEY_PAIR_BASIC when the other is enabled.
• Do the right thing for other PSA_WANT_KEY_TYPE_DH_KEY_PAIR_xxx and PSA_WANT_KEY_TYPE_DH_PUBLIC_KEY.

Note: is this auto-enabling what we want? Another way to handle this is acceptable if we decide that the goal listed here isn't the best architectural choice.