build: bump agent-js v0.20.2

[krpeacock]

Motivation

Bump agent-js v0.20.2 without breaking changes - i.e. by disabling per default verifyQuerySignatures

PRs

• feat: bump agent-js v0.20.2 with verifyQuerySignatures as an opt-in feature ic-js#499

Changes

Tests

Todos

• Add entry to changelog (if necessary).

[krpeacock]

As it turns out, two changes were required:

• changing private rawKey and derKey into public
• updating the signature of a Princpal's JSON encoding (per fix: Principal JSON is compatible with @dfinity/utils jsonReviver helper agent-js#770)

I also have included the following optional suggestions:

• make use of bufEquals and concat utils from agent-js
• add a from constructor on Secp256k1PublicKey
• Use the Secp256k1PublicKey.from constructor instead of casting using as
• Inject the __derEncodedPublicKey__ value for DerEncodedPublicKeys instead of relying on just the typing

[peterpeterparker]

Due to the timezone difference and the fact that this PR originates from a fork, I took the liberty to open a new PR to complete the implementation based on your code. I copied your key implementation without making any further changes. I hope this makes sense.

This continues there 👉 #4068