Further Credentials-related clean-up

Additional clean-up work related to removal of screenlock dependency
from the credentials installation flow:
* Move the CredentialStorage class to security/ so that Enterprise team
  owners could review changes to it.
* Remove the ConfigureKeyGuardDialog class as it is no longer used.
* Remove attempt to unlock KeyStore from VPN settings.
* Remove intents that will no longer be sent from the manifest.

Bug: 120901345
Test: m -j RunSettingsRoboTests
Test: Manual with CtsVerifier
Change-Id: Ia708ede3366892d74c148f3712a63858d5ab53b7
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index a12c982..0f15d71 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -1249,12 +1249,11 @@
                   android:label="@string/local_backup_password_title"
                   android:exported="false" />
 
-        <activity android:name="CredentialStorage"
+        <activity android:name=".security.CredentialStorage"
                 android:theme="@style/Transparent"
                 android:launchMode="singleTop"
                 android:configChanges="orientation|keyboardHidden|screenSize">
             <intent-filter android:priority="1">
-                <action android:name="com.android.credentials.UNLOCK" />
                 <action android:name="com.android.credentials.INSTALL" />
                 <action android:name="com.android.credentials.RESET" />
                 <category android:name="android.intent.category.DEFAULT" />