Use a standard gradle project structure.

I'm going to add tests next, but with this weird file structure I've been using, there's no good place to put them.

The only content changes here are in build.gradle.

PiperOrigin-RevId: 512914783
diff --git a/idea_plugin/build.gradle b/idea_plugin/build.gradle
index 294d77e..6c9695d 100644
--- a/idea_plugin/build.gradle
+++ b/idea_plugin/build.gradle
@@ -50,13 +50,6 @@
   token = project.ext.properties.jetbrainsPluginRepoToken
 }
 
-sourceSets {
-  main {
-    java.srcDir "src"
-    resources.srcDir "resources"
-  }
-}
-
 dependencies {
   implementation "com.google.googlejavaformat:google-java-format:${googleJavaFormatVersion}"
 }
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/CodeStyleManagerDecorator.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/CodeStyleManagerDecorator.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/CodeStyleManagerDecorator.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/CodeStyleManagerDecorator.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/FormatterUtil.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/FormatterUtil.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/FormatterUtil.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/FormatterUtil.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatCodeStyleManager.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatCodeStyleManager.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatCodeStyleManager.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatCodeStyleManager.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.form b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.form
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.form
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.form
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatConfigurable.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatInstaller.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatInstaller.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatInstaller.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatInstaller.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatSettings.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatSettings.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/GoogleJavaFormatSettings.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/GoogleJavaFormatSettings.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/InitialConfigurationProjectManagerListener.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/InitialConfigurationProjectManagerListener.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/InitialConfigurationProjectManagerListener.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/InitialConfigurationProjectManagerListener.java
diff --git a/idea_plugin/src/com/google/googlejavaformat/intellij/UiFormatterStyle.java b/idea_plugin/src/main/java/com/google/googlejavaformat/intellij/UiFormatterStyle.java
similarity index 100%
rename from idea_plugin/src/com/google/googlejavaformat/intellij/UiFormatterStyle.java
rename to idea_plugin/src/main/java/com/google/googlejavaformat/intellij/UiFormatterStyle.java
diff --git a/idea_plugin/resources/META-INF/plugin.xml b/idea_plugin/src/main/resources/META-INF/plugin.xml
similarity index 100%
rename from idea_plugin/resources/META-INF/plugin.xml
rename to idea_plugin/src/main/resources/META-INF/plugin.xml