Migrate the blkio controller to the v2 cgroup hierarchy

This patch preserves the following parameter values:
* Foreground BFQ weight:      100
* Foreground CFQ group_idle:    0
* Foreground CFQ weight:     1000
* Background BFQ weight:       10
* Background CFQ group_idle:    0
* Background CFQ weight:      200

The foreground BFQ weight in task_profiles.json is the default BFQ
weight. From
https://www.kernel.org/doc/Documentation/block/bfq-iosched.txt

:
"weight (namely blkio.bfq.weight or io.bfq-weight): the weight of the
group inside its parent. Available values: 1..10000 (default 100). The
linear mapping between ioprio and weights, described at the beginning
of the tunable section, is still valid, but all weights higher than
IOPRIO_BE_NR*10 are mapped to ioprio 0."

Bug: 213617178
Test: Booted Android in Cuttlefish and ran the following test:
Test: adb -e shell cat /sys/fs/cgroup/*/*/io.bfq.weight | sort | uniq -c
Test: 22 default 10
Test: 98 default 100
Change-Id: I7dfa521363a316592852fecce9192708c7a90514
Signed-off-by: Bart Van Assche <bvanassche@google.com>