Update the KeyMint feature version to 300

As we've updated the KeyMint version to 3, update the default feature
version to 300. That allows external developers to tell which KeyMint
version is running on the device.

Bug: 244732345
Test: atest android.keystore.cts.DeviceOwnerKeyManagementTest
Change-Id: I9b333eeb77a62a79e8e664d40b5564767643aa3d