Implement fsverity metadata generator

Using fsverity tool, fsverity metadata for specific artifacts in system
mage can be generated. Users can do that by setting a makefile variable
PRODUCT_SYSTEM_FSVERITY_GENERATE_METADATA to true.

If set to true, the following artifacts will be signed.

- system/framework/*.jar
- system/framework/oat/<arch>/*.{oat,vdex,art}
- system/etc/boot-image.prof
- system/etc/dirty-image-objects

One fsverity metadata container file per one input file will be
generated in system.img, with a suffix ".fsv_meta". e.g. a container
file for "system/framework/foo.jar" will be
"system/framework/foo.jar.fsv_meta".

Bug: 193113311
Test: build with PRODUCT_SYSTEM_FSVERITY_GENERATE_METADATA := true
Change-Id: Ib70d591a72d23286b5debcb05fbad799dfd79b94