JVM IR: script is a valid container for local delegated properties

When serializing metadata for local delegated properties, we need to
find a valid container class where to put it, and where kotlin-reflect
will be able to find that metadata at runtime. Taking just the closest
class lexically doesn't work, because in the attached test, it is a
class for a lambda which does not have metadata and thus does not have a
way to store any extra information.

So, in 1663619606 we started to look for the closest "non-synthetic"
class to store this metadata. But apparently it was missed that script
is a valid container class. In the test, this meant that no
non-synthetic container classes were found to store the metadata, so we
falled back to using the closest class anyway (see `?: this` in
`rememberLocalProperty`), which turned out to be the lambda.

After this change, metadata for local delegated property in a lambda
will be stored in the script class, just like it's stored in the file
class in the non-script case.

 #KT-55065 Fixed

compiler/testData/codegen/script/localDelegatedPropertyInLambda.kts

@@ -0,0 +1,17 @@
+// WITH_REFLECT
+
+import kotlin.reflect.KProperty
+
+class Delegate {
+    operator fun getValue(t: Any?, p: KProperty<*>): String =
+        if (p.returnType.toString() == "kotlin.String") "OK" else "Fail: ${p.returnType}"
+}
+
+fun f(lambda: () -> String): String = lambda()
+
+val x = f {
+    val prop: String by Delegate()
+    prop
+}
+
+// expected: x: OK