[K/N] Add kotlinx.cinterop.ExperimentalForeignApi opt-ins

Add more opt-ins in Samples, tests and Benchmarks.
This is a follow-up to KT-MR-9788 

Merge-request: KT-MR-9997
Merged-by: Pavel Punegov <Pavel.Punegov@jetbrains.com>

kotlin-native/backend.native/tests/samples/build.gradle.kts

@@ -21,7 +21,10 @@ allprojects {
     }
 
     tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinNativeCompile>().configureEach {
-        compilerOptions.freeCompilerArgs.add("-XXLanguage:+ImplicitSignedToUnsignedIntegerConversion")
+        compilerOptions.freeCompilerArgs.addAll(
+                "-XXLanguage:+ImplicitSignedToUnsignedIntegerConversion",
+                "-opt-in=kotlinx.cinterop.ExperimentalForeignApi"
+        )
     }
 }