[security-getting-started.adoc & security.adoc] Create a concept topic to explain the Identity Providers in Quarkus

This task is done when:

• *[If there is/will be enough ref information to warrant a dedicated ref topic at this time without going over scope... ] *A new diataxis template concept is created and completed that moves information about   Identity Providers in Quarkus Security topics security-getting-started.adoc and security.adoc.
• Minimal style effort.
• Xrefs and links are updated accordingly throughout the other topics in the repo.
• All is SME approved and merged to main.

 
Original state before poc: https://github.com/quarkusio/quarkus/pull/27009/files?short_path=3b6266f#diff-3b6266f9cc9ea2d5e564f8c57520e0a3f44c5372b5e1b35f624463f5517a8ada

Note: The original security-getting-started.adoc an security.adoc are now spread across these 4 topics:

https://github.com/quarkusio/quarkus/blob/main/docs/src/main/asciidoc/security-basic-authentication-tutorial.adoc
https://github.com/quarkusio/quarkus/blob/main/docs/src/main/asciidoc/security-basic-authentication-howto.adoc
https://github.com/quarkusio/quarkus/blob/main/docs/src/main/asciidoc/security-basic-authentication-concept.adoc

https://github.com/quarkusio/quarkus/blob/main/docs/src/main/asciidoc/security-overview-concept.adoc