implement PQC CLI tests

[falko-strenzke]

See https://github.com/rnpgp/rnp/pull/2126#issuecomment-1735062122 (continue branch pqc-cli-tests)

• [x] make PR to parent project (once all tests are running through)
• [x] CLI tests generate and use key:
  • [x] w/ and w/o password for secret key
  • [x] sign / verify tests
  • [x] encrypt / decrypt tests
  • [x] encrypt to v6 key
  • [x] encrypt to v4 key (implies encrypting to v1 SEIPD, as Features Subpacket is absent)
  • [x] for all algorithms
  • [x] for all SPHINCS⁺ parameters (in the current pqc-draft)

[falko-strenzke]

Estimate the effort

[falko-strenzke]

Now implemented feature that testing PQC scheme is dependent on output of rnp --version.

For instance at the end of the output from ctest -V -R cli_tests-Encryption, the list of the determined features is displayed. At the very bottom one finds the indication of the PQC support.

285: GPG_AEAD_EAX: False
285: GPG_AEAD_OCB: False
285: GPG_NO_OLD: False
285: GPG_BRAINPOOL: True
285: RNP_TWOFISH: True
285: RNP_BLOWFISH: True
285: RNP_IDEA: True
285: RNP_CAST5: True
285: RNP_RIPEMD160: True
285: RNP_BRAINPOOL: True
285: RNP_AEAD_EAX: True
285: RNP_AEAD_OCB: True
285: RNP_AEAD_OCB_AES: False
285: RNP_BOTAN_OCB_AV: False
285: RNP_PQC: True