Refactor GraalVM Substitutions for Confluent JSON Schema Serde

This commit moves the GraalVM substitutions related to the Confluent JSON Schema Serde to a dedicated package. Previously, these substitutions caused a split-package issue between the deployment and runtime modules.

Fix #44722

extensions/schema-registry/confluent/json-schema/runtime/src/main/java/io/quarkus/confluent/registry/json/ConfluentJsonSubstitutions.java → extensions/schema-registry/confluent/json-schema/runtime/src/main/java/io/quarkus/confluent/registry/json/runtime/graal/ConfluentJsonSubstitutions.java

@@ -1,4 +1,4 @@
-package io.quarkus.confluent.registry.json;
+package io.quarkus.confluent.registry.json.runtime.graal;
 
 import java.io.IOException;
 import java.util.Arrays;