Upgrade to OpenPGP.js v6

[larabr]

As OpenPGP.js is now declared as "module", we also switch pmcrypto to be one. This causes the majority of changes in this PR.

Non-breaking changes:

• added support for reading and generating v6 packet versions
• added support for processing and generating Curve448 keys, and Curve25519 in new format
• ...

Breaking changes:

• for downstream TS compiler, using the new "node16" or "Bundler" module resolution is required, as e.g. the noble-hashes lib uses exports only (if this is too problematic, we could temporarily add legacy entrypoints to that dependency, since we currently use a fork).
• limited support for (legacy, non-standardized) AEAD-encrypted v4 keys as per draft4880bis
• enum name changes related to legacy curve25519 and eddsa
• ...

TODO:

• [x] rebase on top of TS fix for lightweight build (to be released in next openpgpjs v6 pre-release)
• [ ] release protontech/v6 and point to it
• [x] test integration with web-clients, esp. TS config
• post-canary:
  • [ ] we currently reject keys in new eddsa/xecdh format (in checkKeyStrength)
  • [ ] accept sha3 in generated key prefs
  • [ ] make explicit date inputs mandatory?
• [ ] ...