Fix TerminalProvider sorting

- Change provider sorting so that it uses provider name instead
  of provider object itself. This fixes getting a proper sorting
  list index to compare the order. Uses null check in case provider
  wrongly gives name as null.
- Fixes #846, #852

terminal/src/main/java/org/jline/terminal/TerminalBuilder.java

@@ -404,7 +404,7 @@ private Terminal doBuild() throws IOException {
         List<String> order = Arrays.asList(
                 System.getProperty(PROP_PROVIDERS, PROP_PROVIDERS_DEFAULT).split(","));
         providers.sort(Comparator.comparing(l -> {
-            int idx = order.indexOf(l);
+            int idx = order.indexOf(l.name());
             return idx >= 0 ? idx : Integer.MAX_VALUE;
         }));