Replace JCenter with Maven Central. (#1057)

On February 3 2021, JFrog [announced](https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/) the shutdown of JCenter. Later on April 27 2021, an update was provided that the repository will only be read only and new package and versions are no longer accepted on JCenter.  This means we should no longer use JCenter for our central artifacts repository.

This change replaces JCenter with Maven Central as per the Gradle recommendation - https://blog.gradle.org/jcenter-shutdown

Signed-off-by: Rabi Panda <adnapibar@gmail.com>

buildSrc/build.gradle

@@ -94,7 +94,8 @@ tasks.withType(JavaCompile).configureEach {
  *****************************************************************************/
 
 repositories {
-  jcenter()
+  mavenCentral()
+  gradlePluginPortal()
 }
 
 dependencies {

buildSrc/src/integTest/groovy/org/opensearch/gradle/OpenSearchTestBasePluginFuncTest.groovy

@@ -53,7 +53,7 @@ class OpenSearchTestBasePluginFuncTest extends AbstractGradleFuncTest {
             }
 
             repositories {
-                jcenter()
+                mavenCentral()
             }
 
             dependencies {

buildSrc/src/main/java/org/opensearch/gradle/RepositoriesSetupPlugin.java

@@ -82,7 +82,7 @@ public class RepositoriesSetupPlugin implements Plugin<Project> {
             // such that we don't have to pass hardcoded files to gradle
             repos.mavenLocal();
         }
-        repos.jcenter();
+        repos.mavenCentral();
 
         String luceneVersion = VersionProperties.getLucene();
         if (luceneVersion.contains("-snapshot")) {

buildSrc/src/testKit/opensearch.build/build.gradle

@@ -39,7 +39,7 @@ repositories {
       artifact()
     }
   }
-  jcenter()
+  mavenCentral()
 }
 
 repositories {
@@ -53,7 +53,7 @@ repositories {
       artifact()
     }
   }
-  jcenter()
+  mavenCentral()
 }
 
 // todo remove offending rules

buildSrc/src/testKit/testingConventions/build.gradle

@@ -18,7 +18,7 @@ allprojects {
   apply plugin: 'opensearch.build'
 
   repositories {
-    jcenter()
+    mavenCentral()
   }
   dependencies {
     testImplementation "junit:junit:4.13.1"

buildSrc/src/testKit/thirdPartyAudit/build.gradle

@@ -36,7 +36,7 @@ repositories {
       artifact()
     }
   }
-  jcenter()
+  mavenCentral()
 }
 
 dependencies {