updates to enveloping and JSON serialization

[bc-pi]

-Update JSON Serialization to remove the kb_jwt member and allow for the disclosures to be conveyed elsewhere -Expand the Enveloping SD-JWTs section to also discuss enveloping JSON serialized SD-JWTs -Swap Enveloping SD-JWTs and JSON Serialization sections

Editor's Copy from this PR: https://drafts.oauth.net/oauth-selective-disclosure-jwt/bc/enveloping-n-serialization/draft-ietf-oauth-selective-disclosure-jwt.html#name-jws-json-serialization https://drafts.oauth.net/oauth-selective-disclosure-jwt/bc/enveloping-n-serialization/draft-ietf-oauth-selective-disclosure-jwt.html#name-enveloping-sd-jwts

[Sakurann]

I think this also addresses #325