Include guide in config model generated by extension annotation processor when available

[gsmet]

Description

We already read the metadata when available, we could potentially include the guide.

Note that it would only be available in the runtime artifact so we need a way to document that this information needs to be taken from the runtime artifact, even for the deployment config.

Implementation ideas

No response

[quarkus-bot]

/cc @radcortez (config)

[gsmet]

Actually, it's probably better to consume it from the extension metadata file directly.