[platform] properly update the value of 'ide.experimental.ui' property in early-access-registry.txt (GTW-5443, GTW-5437)

EarlyAccessRegistryManager saves only values of properties which were accessed via it. So if we set a new value for some property before it was accessed, it won't be saved to early-access-registry.txt file.

GitOrigin-RevId: 8bb9cbd457d9eba3169db88e9b9a2a80658ec157

platform/core-api/src/com/intellij/openapi/util/registry/EarlyAccessRegistryManager.kt

@@ -113,6 +113,15 @@ object EarlyAccessRegistryManager {
     saveConfigFile(map, configFile) { map.get(it) }
   }
 
+  /**
+   * Updates value for registry property which may be accessed via this class. 
+   * Use this function instead of the default [RegistryValue.setValue] to ensure that the updated value will be saved to [fileName]. 
+   */
+  fun setBoolean(key: String, value: Boolean) {
+    lazyMap.value[key] = value.toString()
+    ApplicationManager.getApplication().serviceIfCreated<RegistryManager>()?.get(key)?.setValue(value)
+  }
+  
   fun syncAndFlush() {
     // Why do we sync? get (not yet loaded) -> not changed by a user but actually in a registry -> no explicit put
     // Why maybe in a registry but not in our store?

platform/lang-impl/src/com/intellij/ui/ExperimentalUIImpl.kt

@@ -19,7 +19,6 @@ import com.intellij.openapi.diagnostic.logger
 import com.intellij.openapi.ui.MessageDialogBuilder
 import com.intellij.openapi.ui.Messages
 import com.intellij.openapi.util.registry.EarlyAccessRegistryManager
-import com.intellij.openapi.util.registry.Registry
 import com.intellij.util.PlatformUtils
 
 /**
@@ -114,7 +113,7 @@ private class ExperimentalUIImpl : ExperimentalUI() {
   private fun saveNewValue(enabled: Boolean) {
     try {
       logger.info("Saving newUi=$enabled to registry")
-      Registry.get(KEY).setValue(enabled)
+      EarlyAccessRegistryManager.setBoolean(KEY, enabled)
       EarlyAccessRegistryManager.syncAndFlush()
     }
     catch (e: Throwable) {