[kotlin] enable Kotlin plugin K2 mode by default in Nightly

The behavior with the `idea.kotlin.plugin.use.k2` VM option will be the following:
- When no `idea.kotlin.plugin.use.k2` is specified in `.vmoptions`, it will be implicitly set to `true`.
- If `idea.kotlin.plugin.use.k2` is set to `true`/`false` in `.vmoptions`, this value will be used.
- If a user disables K2 mode manually in the settings, then `idea.kotlin.plugin.use.k2` will be set to `false` in `.vmoptions` and the K2 mode will be considered as disabled after a restart.

^KTIJ-30761 fixed

GitOrigin-RevId: bdafaad289b4e6ad3600f0653b336aefde20874f

build/src/org/jetbrains/intellij/build/IdeaCommunityProperties.kt

@@ -81,6 +81,7 @@ open class IdeaCommunityProperties(private val communityHomeDir: Path) : BaseIde
     buildDocAuthoringAssets = true
 
     qodanaProductProperties = QodanaProductProperties("QDJVMC", "Qodana Community for JVM")
+    enableKotlinPluginK2ByDefault()
   }
 
   override suspend fun copyAdditionalFiles(context: BuildContext, targetDir: Path) {

platform/build-scripts/src/org/jetbrains/intellij/build/BaseIdeaProperties.kt

@@ -170,4 +170,12 @@ abstract class BaseIdeaProperties : JetBrainsProductProperties() {
     additionalModulesToCompile = persistentListOf("intellij.tools.jps.build.standalone")
     modulesToCompileTests = persistentListOf("intellij.platform.jps.build.tests")
   }
+
+  /**
+   * 🌲
+   * see KTIJ-30761
+   */
+  protected fun enableKotlinPluginK2ByDefault() {
+    additionalVmOptions += "-Didea.kotlin.plugin.use.k2=true"
+  }
 }