Is your feature request related to a problem? Please describe.

you can refer to https://www.postgresql.org/docs/current/pgcrypto.html#PGCRYPTO-PGP-ENC-FUNCS

related impl in postgres source code: https://github.com/postgres/postgres/blob/REL_16_1/contrib/pgcrypto/pgp-encrypt.c & https://github.com/postgres/postgres/blob/REL_16_1/contrib/pgcrypto/pgp-decrypt.c

related tests in postgres: https://github.com/postgres/postgres/blob/REL_16_1/contrib/pgcrypto/sql/pgp-decrypt.sql & https://github.com/postgres/postgres/blob/REL_16_1/contrib/pgcrypto/sql/pgp-encrypt.sql & https://github.com/postgres/postgres/blob/REL_16_1/contrib/pgcrypto/sql/pgp-pubkey-decrypt.sql & https://github.com/postgres/postgres/blob/REL_16_1/contrib/pgcrypto/sql/pgp-pubkey-encrypt.sql

You need to:

1. read the context above and understand how pgp encrypt and decrypt impl
2. refer to feat: support sql func encrypt/decrypt  #14717 for similar raw encrypt/decrypt impl, you need to impl all pgp_sym_encrypt , pgp_sym_decrypt , pgp_pub_encrypt and pgp_pub_decrypt
3. apply all related tests from postgres and make sure the feature give the same result as postgres does.

Describe the solution you'd like

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Describe alternatives you've considered

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Additional context

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