Add F2FS support for apexd

Filesystem type used for apex_payload is retrieved when opening an APEX.
Magic bytes are read are the expected offset in the filesystem.
If neither f2fs magic nor ext4 magic can be found, it fails.

Test: boot successfuly with ext4 apexes
install succesfuly ext4 / f2fs apexes
atest ApexTestCases

Bug: 158453869

Change-Id: If8eb9f6f28f81cdb0915c63f51482827138bf9f8
Merged-In: If8eb9f6f28f81cdb0915c63f51482827138bf9f8
6 files changed