Improve JWK into PublicKey conversions

[curtis-h]

Proposed feature

Improve how we convert JWK objects into PublicKey instances.
For instance in JWTCore.ts we explicitly convert based on several conditionals, which may or may not be according spec.

Does this belong in Apollo?

Feature description

We should follow JWK spec to parse the values, ie x which could describe a co-ord or key data; dependent on the type of JWT.
And from there create the relevant Key.

Anything else?

No response