Migrate header to expect in libraries projects

libraries/kotlin.test/common/src/main/kotlin/kotlin/test/AssertionsH.kt

@@ -6,7 +6,7 @@ import kotlin.reflect.KClass
  * Comments out a block of test code until it is implemented while keeping a link to the code
  * to implement in your unit test output
  */
-header fun todo(block: () -> Unit)
+expect fun todo(block: () -> Unit)
 
 /** Asserts that a [block] fails with a specific exception of type [exceptionClass] being thrown. */
-header fun <T : Throwable> assertFailsWith(exceptionClass: KClass<T>, message: String?, block: () -> Unit): T
+expect fun <T : Throwable> assertFailsWith(exceptionClass: KClass<T>, message: String?, block: () -> Unit): T

libraries/kotlin.test/common/src/main/kotlin/kotlin/test/Utils.kt

@@ -1,7 +1,7 @@
 package kotlin.test
 
 internal fun messagePrefix(message: String?) = if (message == null) "" else "$message. "
-internal header fun lookupAsserter(): Asserter
+internal expect fun lookupAsserter(): Asserter
 
 @PublishedApi // required to get stable name as it's called from box tests
 internal fun overrideAsserter(value: Asserter?): Asserter? {

libraries/kotlin.test/common/src/main/kotlin/org/junit/Test.kt

@@ -1,4 +1,4 @@
 package org.junit
 
 @Suppress("NO_ACTUAL_FOR_EXPECT")
-header annotation class Test
+expect annotation class Test