CHROMIUM: chromiumos: Add policy for blk-crypto passthrough

Annotate inodes with an attribute that allows block I/O from those
inodes to be passed through blk-crypto. This is useful for inline
encryption setups where the underlying layer has encryption but
the files might require unencrypted usage.

BUG=b:376100765, b:376099411
UPSTREAM-TASK=b:391902360
TEST=USE=default_key_stateful, add /mnt/stateful_partition/unencrypted
    1. write to /mnt/stateful_partition/unencrypted/a.txt
    2. filefrag -v a.txt to get extents
    3. hexdump -C -n 100 --skip <extent start> /dev/nvme0n1p1
    4. Validate contents have been passed through

Signed-off-by: Sarthak Kukreti <sarthakkukreti@google.com>
Change-Id: I7a2aca71e2863957b2bb1753597600752f21b5da
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/5926146


Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Thomas Cedeno <thomascedeno@google.com>
Signed-off-by: Hubert Mazur <hmazur@google.com>