Fix running stdlib tests in worker on Native

Add `@SharedImmutable` or `@ThreadLocal` where required.

libraries/stdlib/test/text/StringTest.kt

@@ -11,6 +11,7 @@ import test.collections.behaviors.iteratorBehavior
 import test.collections.behaviors.setBehavior
 import test.collections.compare
 import kotlin.math.sign
+import kotlin.native.concurrent.SharedImmutable
 import kotlin.random.Random
 
 
@@ -18,6 +19,7 @@ fun createString(content: String): CharSequence = content
 fun createStringBuilder(content: String): CharSequence = StringBuilder((content as Any).toString()) // required for Rhino JS
 
 
+@SharedImmutable
 val charSequenceBuilders = listOf(::createString, ::createStringBuilder)
 
 fun withOneCharSequenceArg(f: ((String) -> CharSequence) -> Unit) {