xfs: Check for extent overflow when growing realtime bitmap/summary inodes

Verify that XFS does not cause realtime bitmap/summary inode fork's
extent count to overflow when growing the realtime volume associated
with a filesystem.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>

tests/xfs/530.out

@@ -0,0 +1,11 @@
+QA output created by 530
+* Test extending rt inodes
+Create fake rt volume
+Format and mount rt volume
+Consume free space
+Create fragmented filesystem
+Inject reduce_max_iextents error tag
+Inject bmap_alloc_minlen_extent error tag
+Grow realtime volume
+Verify rbmino's and rsumino's extent count
+Check filesystem