Explicitly use language version 1.9 for K2-unsupported parts

This commit explicitly sets LV 1.9 for all projects with disabled FIR
bootstrap, as well as for libraries, including Native stdlib.

Related to KT-59171

kotlin-native/runtime/build.gradle.kts

@@ -589,6 +589,8 @@ konanArtifacts {
                 "-opt-in=kotlin.contracts.ExperimentalContracts",
                 "-opt-in=kotlin.ExperimentalMultiplatform",
                 "-opt-in=kotlin.native.internal.InternalForKotlinNative",
+                "-language-version",
+                "1.9",
         )
 
         commonStdlibSrcDirs.forEach { commonSrcDir(it) }