feat(jwt) : add feature to jwt plugin:allow set headers from claim

[mtparet]

Summary Add feature to jwt plugin: allow set header from claims.

Reopenning of https://github.com/Kong/kong/pull/4761 https://github.com/Kong/kong/pull/5713

Full changelog

[Implement] jwt plugin: allow set header from claims
if you configure headers_to_set(set) , headers with prefix "X-Jwt-Claim-" will be set to the response. For example, if 'sub' and 'app' are configured, and both of them are found in jwt's claims, two headers will be set to the response: X-Jwt-Claim-Sub and X-Jwt-Claim-App.