Moving recovery resources from /system to /vendor

This change is part of a topic that moves the recovery resources from the
system partition to the vendor partition, if it exists, or the vendor directory
on the system partition otherwise. The recovery resources are moving from the
system image to the vendor partition so that a single system image may be used
with either an A/B or a non-A/B vendor image. The topic removes a delta in the
system image that prevented such reuse in the past.

The recovery resources that are moving are involved with updating the recovery
partition after an update. In a non-A/B configuration, the system boots from
the recovery partition, updates the other partitions (system, vendor, etc.)
Then, the next time the system boots normally, a script updates the recovery
partition (if necessary). This script, the executables it invokes, and the data
files that it uses were previously on the system partition. The resources that
are moving include the following.

* install-recovery.sh
* applypatch
* recovery-resource.dat (if present)
* recovery-from-boot.p (if present)

This change moves the recovery resources to vendor in libcutils/fs_config.cpp
and removes the flash_recovery service from rootdir/init.rc. This service moved
to a vendor init.rc file in bootable/recovery/applypatch.

Bug: 68319577
Test: Ensure that recovery partition is updated correctly.
Change-Id: I492f7989ea8042912e9d0e0eadeaa351affbee13