Rename AbstractTheiaCloudOperator to BasicTheiaCloudOperator

Also remove the abstract so it can directly be used.
Use it directly in the DefaultTheiaCloudOperatorModule.
Remove the DefaultTheiaCloudOperator as it is no longer needed.
Extract LeaderElection in separate method for easier customization.
Also make the other methods in the leader election protected.

java/operator/org.eclipse.theia.cloud.defaultoperator/src/main/java/org/eclipse/theia/cloud/defaultoperator/DefaultTheiaCloudOperatorModule.java

@@ -16,6 +16,7 @@
  ********************************************************************************/
 package org.eclipse.theia.cloud.defaultoperator;
 
+import org.eclipse.theia.cloud.operator.BasicTheiaCloudOperator;
 import org.eclipse.theia.cloud.operator.TheiaCloudOperator;
 import org.eclipse.theia.cloud.operator.TheiaCloudOperatorArguments;
 import org.eclipse.theia.cloud.operator.di.AbstractTheiaCloudOperatorModule;
@@ -28,7 +29,7 @@ public DefaultTheiaCloudOperatorModule(TheiaCloudOperatorArguments arguments) {
 
     @Override
     protected Class<? extends TheiaCloudOperator> bindTheiaCloudOperator() {
-	return DefaultTheiaCloudOperator.class;
+	return BasicTheiaCloudOperator.class;
     }
 
 }