Ruby: Make similar changes to differentiate extraction errors and warnings, and mostly restore original behaviour.

ruby/ql/lib/codeql/files/FileSystem.qll

@@ -2,6 +2,7 @@
 
 private import codeql.Locations
 private import codeql.util.FileSystem
+private import codeql.ruby.Diagnostics
 
 private module Input implements InputSig {
   abstract class ContainerBase extends @container {
@@ -34,3 +35,20 @@ class File extends Container, Impl::File {
   /** Holds if this file was extracted from ordinary source code. */
   predicate fromSource() { any() }
 }
+
+/**
+ * A successfully extracted file, that is, a file that was extracted and
+ * contains no extraction errors or warnings.
+ */
+class SuccessfullyExtractedFile extends File {
+  SuccessfullyExtractedFile() {
+    not exists(Diagnostic d |
+      d.getLocation().getFile() = this and
+      (
+        d instanceof ExtractionError
+        or
+        d instanceof ExtractionWarning
+      )
+    )
+  }
+}