Mark expect/actual classifiers as experimental

^KT-61573 Fixed
Review: https://jetbrains.team/p/kt/reviews/11969/timeline

Tests:
- MultiPlatformIntegrationTestGenerated
- CliTestGenerated
- MultiPlatformIntegrationTestGenerated
- DiagnosticTestGenerated.Multiplatform
- FirLightTreeOldFrontendDiagnosticsTestGenerated

Also add -Xexpect-actual-classes flag to all necessary ./libraries/* modules
Otherwise compilation of those modules failes because of `-Werror`

repo/gradle-build-conventions/buildsrc-compat/src/main/kotlin/wasm/wasmKotlinTest.kt

@@ -85,6 +85,7 @@ fun Project.configureWasmKotlinTest(
     tasks.withType<KotlinCompile<*>>().configureEach {
         kotlinOptions.freeCompilerArgs += listOf(
             "-Xallow-kotlin-package",
+            "-Xexpect-actual-classes",
             "-opt-in=kotlin.ExperimentalMultiplatform",
             "-opt-in=kotlin.contracts.ExperimentalContracts",
             "-Xwasm-target=$wasmTargetParameter"

repo/gradle-build-conventions/buildsrc-compat/src/main/kotlin/wasm/wasmStdLib.kt

@@ -146,6 +146,7 @@ fun Project.configureWasmStdLib(
     tasks.withType<KotlinCompile<*>>().configureEach {
         kotlinOptions.freeCompilerArgs += listOf(
             "-Xallow-kotlin-package",
+            "-Xexpect-actual-classes",
             "-opt-in=kotlin.ExperimentalMultiplatform",
             "-opt-in=kotlin.contracts.ExperimentalContracts",
             "-opt-in=kotlin.RequiresOptIn",