xfs: improve metadata array field handling when fuzzing

xfs: improve metadata array field handling when fuzzing

Currently, we use some gnarly regular expressions to try to constrain
the amount of time we spend fuzzing each element of a metadata array.
This is pretty inflexible (and buggy) since we limit some arrays
(e.g. dir hashes) to the first ten elements and other arrays (e.g.
extent mappings) that use compact index ranges to the first one.

Replace this whole weird mess with logic that can tease out the array
indices, unroll the compact indices if needed, and give the user more
flexible control over which array elements get used.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>