Native: enable HMPP in tests/samples

Remove `kotlin.mpp.hierarchicalStructureSupport=false`.
Disabling HMPP is not supported anymore.

^KT-59304

kotlin-native/backend.native/tests/samples/echoServer/src/echoServerMain/kotlin/EchoServer.kt

@@ -30,6 +30,7 @@ fun main(args: Array<String>) {
 
         with(serverAddr) {
             memset(this.ptr, 0, sockaddr_in.size.convert())
+            @OptIn(UnsafeNumber::class)
             sin_family = AF_INET.convert()
             sin_port = posix_htons(port).convert()
         }

kotlin-native/backend.native/tests/samples/gradle.properties

@@ -16,6 +16,3 @@ kotlin.native.home=../../dist
 
 # Increase memory for in-process compiler execution.
 org.gradle.jvmargs=-Xmx3g
-
-# Disable HMPP with metadata until KT-50547 is not fixed
-kotlin.mpp.hierarchicalStructureSupport=false