Unhide getKey() and importKey() and the whole class of RecoveryController.

Added @RequiresPermission(android.permission.RECOVER_KEYSTORE) on all
public APIs of RecoveryController.

Bug: 73900159
Test: adb shell am instrument -w -e package \
com.android.server.locksettings.recoverablekeystore \
com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner

Change-Id: I1047c038603869307d7a2462a2e5635fcd1c94c2