Migrate UseExperimental->OptIn in project sources

compiler/tests/org/jetbrains/kotlin/daemon/experimental/integration/CompilerDaemonTest.kt

@@ -778,7 +778,7 @@ class CompilerDaemonTest : KotlinIntegrationTestBase() {
     private val PARALLEL_THREADS_TO_COMPILE = 10
     private val PARALLEL_WAIT_TIMEOUT_S = 60L
 
-    @UseExperimental(ObsoleteCoroutinesApi::class)
+    @OptIn(ObsoleteCoroutinesApi::class)
     private fun runCompile(
         daemon: CompileServiceAsync,
         resultCodes: Array<Int?>,
@@ -878,7 +878,7 @@ class CompilerDaemonTest : KotlinIntegrationTestBase() {
         const val connectionFailedErr = -100
     }
 
-    @UseExperimental(ObsoleteCoroutinesApi::class)
+    @OptIn(ObsoleteCoroutinesApi::class)
     fun ignore_testParallelDaemonStart() {
 
         val doneLatch = CountDownLatch(ParallelStartParams.threads)

compiler/tests/org/jetbrains/kotlin/daemon/experimental/unit/ConnectionsTest.kt

@@ -352,7 +352,7 @@ class ConnectionsTest : KotlinIntegrationTestBase() {
                 val servicesClient = services.clientSide
                 val compResultsClient = kotlinCompilerClient.createCompResults().clientSide
                 val threadCount = 10
-                @UseExperimental(ObsoleteCoroutinesApi::class)
+                @OptIn(ObsoleteCoroutinesApi::class)
                 fun runThread(i: Int) =
                     async(newSingleThreadContext("thread_$i")) {
                         val jar = tmpdir.absolutePath + File.separator + "hello.$i.jar"