Support OIDC JsonWebKeySet providers

[sberyozkin]

Description

Currently, the process of retrieving JWK sets from the OIDC provider can not be customized. However, as discussed at #36563, it may be necessary in some cases, for example, when a custom authentication mechanism is involved. Or, perhaps, someone would like to fetch the keys from the alternative source (not from the standard OIDC JWKS endpoint).

Implementation ideas

Introduce an interface like

public interface JsonWebKeySetProvider {
    Uni<JsonWebKeySet> getKeys(WebClient client, OidcTenantConfig config, OidcConfigurationMetadata discoveredConfig);
    Uni<JsonWebKeySet> refreshKeys(WebClient client, OidcTenantConfig config, OidcConfigurationMetadata discoveredConfig);
}

CC @calvernaz

and let uses customize the key acquisition process if they need to

[quarkus-bot]

/cc @pedroigor (oidc)

[sberyozkin]

There is a simpler but also more generic way that can be of use to OIDC client operating in quarkus-oidc and quarkus-oidc-client.
Closing for now as not planned