[FE] Add missing 'ClassId' check in Kotlin class loading (KTIJ-23435)

'findKotlinClassOrContent()' does not really distinguish between
outer class names and package path components, so it might return
'foo/bar/Baz.Boo' for 'foo/bar/Baz/Boo'. Possibly because
 'findKotlinClassOrContent()' potentially returns a raw byte array,
 ClassId checking is supposed to be performed in
 'extractClassMetadata()'. For Java, it happens inside
 'FirJavaFacade.findClass()', yet for Kotlin the check was absent.

compiler/testData/codegen/box/package/packageOrNestedClass.kt

@@ -0,0 +1,31 @@
+// TARGET_BACKEND: JVM_IR
+// FIR_IDENTICAL
+
+// MODULE: lib
+
+// FILE: lib.kt
+@file:Suppress("PACKAGE_OR_CLASSIFIER_REDECLARATION")
+package lib
+
+class foo {
+    class bar {
+        fun get(): Int = 1
+    }
+}
+
+// FILE: lib_foo.kt
+@file:Suppress("PACKAGE_OR_CLASSIFIER_REDECLARATION")
+package lib.foo
+
+class bar {
+    fun get(): Int = 0
+}
+
+// MODULE: main(lib)
+
+// FILE: test.kt
+
+fun box(): String {
+    val obj = lib.foo.bar()
+    return if (obj.get() == 0) "OK" else "ERROR"
+}