fstests: add tool migrate group membership data to test files

fstests: add tool migrate group membership data to test files

Create a tool to migrate the mapping of tests <-> groups out of the
group file and into the individual test file as a _begin_fstest
call.  In the next patches we'll rewrite all the test files and auto
generate the group files from the tests.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>