Keystore 2.0 SPI: Install legacy Keystore provider as AndroidKeyStoreLegacy

With this patch we install the old Keystore provider as
AndroidKeyStoreLegacy when the Keystore 2.0 provider is installed as
AndroidKeyStore. This allows system components to keep using the old
keystore while we can run CTS tests against the new provider.

The tests are still mostly failing at this point. Installing the new SPI
can be enabled by setting the property
ro.android.security.keystore2.enable=true

Bug: 159476414
Test: This enables running CTS tests against Keystore 2.0.
Change-Id: I9731d9783ccf8f2705a5ca7335e00c8f4c8debba