Password constraints cleanup.

Unified password validation code between DPMS and Settings.

Bug: 138375712
Test: atest tests/robotests/src/com/android/settings/password/ChooseLockPasswordTest.java
Change-Id: I55e4dae47526659594af3fcdbfc1292edceb5807

src/com/android/settings/password/ChooseLockGenericController.java

@@ -92,6 +92,7 @@ public class ChooseLockGenericController {
      */
     public int upgradeQuality(int quality) {
         // Compare specified quality and dpm quality
+        // TODO(b/142781408): convert from quality to credential type once PIN is supported.
         int dpmUpgradedQuality = Math.max(quality, mDpm.getPasswordQuality(null, mUserId));
         return Math.max(dpmUpgradedQuality,
                 PasswordMetrics.complexityLevelToMinQuality(mRequestedMinComplexity));