KTIJ-37664 [kotlin] Use dropSynchronously in KtCompilerPluginsProviderIdeImpl to drop pluginsCacheCachedValue

This allows the explicit disposal of `KtCompilerPluginsProviderIdeImpl`
to wait until the initialization of `pluginsCacheCachedValue` has finished.

It is not the best solution, because ideally, nobody from the outside
should call the `dispose` function directly on their own.

Unfortunately, `kotlin-rpc` plugin has to do that at the moment,
since it has to download jars with compiler plugins from the network,
and at some point should be able to present a renewed versions of bundled
jars from its `KotlinBundledFirCompilerPluginProvider` implementation.

To address that in the future, please see KTIJ-37667.

^KTIJ-37664 Fixed

GitOrigin-RevId: 867ebe0d1d8df902d1f6ecd5ec6b2cc7f5b54999

plugins/kotlin/fir/src/org/jetbrains/kotlin/idea/fir/extensions/KtCompilerPluginsProviderIdeImpl.kt

@@ -103,9 +103,16 @@ internal class KtCompilerPluginsProviderIdeImpl(
     /**
      * Throws away the cache for all the registered plugins, and executes all the disposables
      * registered in the corresponding [CompilerPluginRegistrar.ExtensionStorage]s.
+     *
+     * Note: we drop the [pluginsCacheCachedValue] synchronously, so that
+     * the [KtCompilerPluginsCache.new] call and all the calls to [KotlinBundledFirCompilerPluginProvider.provideBundledPluginJar] in it
+     * either have not yet started, or have already completed.
+     *
+     * Otherwise, race conditions similar to KTIJ-37664 may occur.
      */
     private fun resetPluginsCache() {
-        pluginsCacheCachedValue.drop()?.dispose()
+        val cache = pluginsCacheCachedValue.dropSynchronously()
+        cache?.dispose()
     }
 
     companion object {