Move cache provider into proper package. (#447)

The cache provider modules source files were previously packaged under the 
`spring.pulsar.core` name. This moves them to a package name that is 
specific to their module name. The motivation of the change is to 
preemptively reduce confusion w/ the Java module system.

Author: onobc

spring-pulsar-cache-provider-caffeine/src/main/java/org/springframework/pulsar/core/CaffeineCacheProvider.java renamed to spring-pulsar-cache-provider-caffeine/src/main/java/org/springframework/pulsar/cache/provider/caffeine/CaffeineCacheProvider.java

@@ -14,12 +14,14 @@
  * limitations under the License.
  */
 
-package org.springframework.pulsar.core;
+package org.springframework.pulsar.cache.provider.caffeine;
 
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 
+import org.springframework.pulsar.cache.provider.CacheProvider;
+
 import com.github.benmanes.caffeine.cache.Cache;
 
 /**

spring-pulsar-cache-provider-caffeine/src/main/java/org/springframework/pulsar/core/CaffeineCacheProviderFactory.java renamed to spring-pulsar-cache-provider-caffeine/src/main/java/org/springframework/pulsar/cache/provider/caffeine/CaffeineCacheProviderFactory.java

@@ -14,10 +14,13 @@
  * limitations under the License.
  */
 
-package org.springframework.pulsar.core;
+package org.springframework.pulsar.cache.provider.caffeine;
 
 import java.time.Duration;
 
+import org.springframework.pulsar.cache.provider.CacheProvider;
+import org.springframework.pulsar.cache.provider.CacheProviderFactory;
+
 import com.github.benmanes.caffeine.cache.Cache;
 import com.github.benmanes.caffeine.cache.Caffeine;
 import com.github.benmanes.caffeine.cache.RemovalListener;

spring-pulsar-cache-provider-caffeine/src/main/resources/META-INF/services/org.springframework.pulsar.cache.provider.CacheProviderFactory

@@ -0,0 +1 @@
+org.springframework.pulsar.cache.provider.caffeine.CaffeineCacheProviderFactory

spring-pulsar-cache-provider-caffeine/src/main/resources/META-INF/services/org.springframework.pulsar.core.CacheProviderFactory

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.pulsar.core;
+package org.springframework.pulsar.cache.provider;
 
 import java.util.Map;
 import java.util.function.BiConsumer;

spring-pulsar-cache-provider/src/main/java/org/springframework/pulsar/core/CacheProvider.java renamed to spring-pulsar-cache-provider/src/main/java/org/springframework/pulsar/cache/provider/CacheProvider.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.pulsar.core;
+package org.springframework.pulsar.cache.provider;
 
 import java.time.Duration;
 import java.util.ServiceLoader;

spring-pulsar-cache-provider/src/main/java/org/springframework/pulsar/core/CacheProviderFactory.java renamed to spring-pulsar-cache-provider/src/main/java/org/springframework/pulsar/cache/provider/CacheProviderFactory.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.pulsar.core;
+package org.springframework.pulsar.cache.provider;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

spring-pulsar-cache-provider/src/test/java/org/springframework/pulsar/core/CacheProviderFactoryTests.java renamed to spring-pulsar-cache-provider/src/test/java/org/springframework/pulsar/cache/provider/CacheProviderFactoryTests.java

@@ -0,0 +1 @@
+org.springframework.pulsar.cache.provider.CacheProviderFactoryTests$TestCacheProviderFactory

spring-pulsar-cache-provider/src/test/resources/META-INF/services/org.springframework.pulsar.cache.provider.CacheProviderFactory

@@ -38,6 +38,8 @@
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.core.log.LogAccessor;
 import org.springframework.lang.Nullable;
+import org.springframework.pulsar.cache.provider.CacheProvider;
+import org.springframework.pulsar.cache.provider.CacheProviderFactory;
 import org.springframework.util.Assert;
 
 /**