[gateway] Improve plan selection based on subscription

[marcambier]

This reports this ticket in 3.18 : #7824

Also, we have to report the breaking change documentation in the upgrade note : https://github.com/gravitee-io/gravitee-docs/blob/master/pages/apim/3.x/installation-guide/upgrades/3.15.14/README.adoc

[LiliaEn]

Tested on 3.18.x env
The following scenarios were covered:

• JWT, API Key, Keyless, oAUth2 plans
• JWT+JWT
• JWT+oAuth2
• API Key+Api Key
• oAUth2+oAuth2 (not working properly without selection rule- it's a known issue on V3)