Migrate from JwsSigned to new JwsCompact

[n0900]

Using JwsCompactTyped not much actually changed except for that it now works better under the hood.
JwsCompactTyped is probably a candidate to move to signum. Dependent on Signum#419. More optimizations using stronger JwsCompact/JwsCompactTyped typing instead of String and new serialization paths are likely possible for many classes but mostly out of scope for this PR because it's already quite huge.

The constructor of JwsCompactTyped cannot be made internal because we need the invoke operators to be inline so that we can infer the payload type on the fly.

I know its conditional on the signum release schedule but as soon as possible please review and merge because this touches nearly every file and merge-conflicts will be horrendous.