deps: add new dependency to gopenpgp

[andyyang890]

This patch adds a new dependency to github.com/ProtonMail/gopenpgp,
which will be used to help implement some of the remaining
unimplemented pgcrypto functions.

Informs #21001

Release note: None

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[knz]

The following dependencies are problematic:

• https://github.com/ProtonMail/go-crypto - implements its own cryptography
• https://github.com/bwesterb/go-ristretto - implements its own cryptography
• https://github.com/cloudflare/circl - implements its own cryptography

There are two major problems with these new dependencies:

• they implement their own cryptography, which is generally a no-no.

  Reference: see all the content available elsewhere already -- https://duckduckgo.com/?q=do+not+implement+your+own+cryptography

  It seems unreasonable to import so much untrusted code doing who-knows-what with cryptography just to implement some esoteric pgcrypto functions. There's a major imbalance in the cost/benefit trade-off.

• they use native Go code, which is not going to be routed to a FIPS-enabled implementation during FIPS builds. This means that all the functionality we'd build on top would not enable FIPS compliance for customers. This is a major deviation from our "Customer Trust" and "Enterprise Readiness" goals for v23.1 and beyond.

[knz]

Internal discussion - https://cockroachlabs.slack.com/archives/CGA9F858R/p1684855555474749
Note that Abhinav is on PTO this week.

[rafiss]

We've decided to deprioritize work on PGP related functions for now.