Make SameNameButDifferent an error

In PalantirJavaFormatSettings `State` named both IntelliJ's @State
annotation and the settings' own State class. The annotation is now
written out in full, which leaves the name to the class.

Author: abashev

buildSrc/src/main/groovy/open-java-format.error-prone-conventions.gradle

@@ -55,6 +55,7 @@ tasks.withType(JavaCompile).configureEach {
 // Checks whose findings have been fixed, build-breaking so that new ones are fixed too rather than read past.
 tasks.withType(JavaCompile).configureEach {
     options.errorprone {
+        error('SameNameButDifferent')
         error('UnusedVariable')
     }
 }

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/PalantirJavaFormatSettings.java

@@ -18,7 +18,6 @@
 
 import com.intellij.formatting.service.FormattingService;
 import com.intellij.openapi.components.PersistentStateComponent;
-import com.intellij.openapi.components.State;
 import com.intellij.openapi.components.Storage;
 import com.intellij.openapi.extensions.PluginDescriptor;
 import com.intellij.openapi.project.Project;
@@ -37,7 +36,7 @@
 
 import static java.util.Optional.ofNullable;
 
-@State(
+@com.intellij.openapi.components.State(
         name = "PalantirJavaFormatSettings",
         storages = {@Storage("open-java-format.xml")})
 public class PalantirJavaFormatSettings implements PersistentStateComponent<PalantirJavaFormatSettings.State> {