Make `quarkus-smallrye-graphql-client` aware of `quarkus-proxy-registry`

[ppalaga]

#50709 brings the new global proxy configuration that works much like TLS registry.
quarkus-smallrye-graphql-client, cf. io.quarkus.smallrye.graphql.client.runtime.GraphQLClientConfig should be made aware of it in a simlar way like reactive REST client in #50709

[quarkus-bot]

/cc @Ladicek (smallrye), @jmartisk (graphql,smallrye), @phillip-kruger (graphql,smallrye), @radcortez (smallrye)

[Ladicek]

Note that I've refactored the Proxy Registry in #50834, so take a look at that too.