Add 'zpool status -e' flag to see unhealthy vdevs

When very large pools are present, it can be laborious to find
reasons for why a pool is degraded and/or where an unhealthy vdev
is. This option filters out vdevs that are ONLINE and with no errors
to make it easier to see where the issues are. Root and parents of
unhealthy vdevs will always be printed.

Sample vdev listings with '-e' option
- Single large pool
	[root@iron5:~]# zpool list
	NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
	iron5   582T  89.7M   582T        -         -     0%     0%  1.00x    ONLINE  -
	[root@iron5:~]# zpool status | wc -l
	97

- All vdevs healthy
	[root@iron5:zfs2.2]# ./zpool status -e
	  pool: iron5
	 state: ONLINE
	  scan: scrub repaired 0B in 00:00:01 with 0 errors on Thu Jan 11 14:40:45 2024
	config:

	    NAME        STATE     READ WRITE CKSUM
	    iron5       ONLINE       0     0     0

	errors: No known data errors

- ZFS errors
	[root@iron5:zfs2.2]# ./zpool status -e
	  pool: iron5
	 state: ONLINE
	status: One or more devices has experienced an error resulting in data
		corruption.  Applications may be affected.
	action: Restore the file in question if possible.  Otherwise restore the
		entire pool from backup.
	   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-8A
	  scan: scrub repaired 24K in 00:00:01 with 1 errors on Thu Jan 11 14:41:27 2024
	config:

		NAME        STATE     READ WRITE CKSUM
		iron5       ONLINE       0     0     0
		  raidz2-5  ONLINE       1     0     0
		    L23     ONLINE       1     0     0
		    L24     ONLINE       1     0     0
		    L37     ONLINE       1     0     0

	errors: 1 data errors, use '-v' for a list

- Vdev faulted
	[root@iron5:zfs2.2]# ./zpool status -e
		pool: iron5
	 state: DEGRADED
	status: One or more devices are faulted in response to persistent errors.
		Sufficient replicas exist for the pool to continue functioning in a
		degraded state.
	action: Replace the faulted device, or use 'zpool clear' to mark the device
		repaired.
	  scan: scrub repaired 0B in 00:00:00 with 0 errors on Thu Jan 11 14:39:42 2024
	config:

		NAME        STATE     READ WRITE CKSUM
		iron5       DEGRADED     0     0     0
		  raidz2-6  DEGRADED     0     0     0
		    L67     FAULTED      0     0     0  too many errors

	errors: No known data errors

- Vdev faults and data errors
[root@iron5:zfs2.2]# ./zpool status -e
  pool: iron5
 state: DEGRADED
status: One or more devices has experienced an error resulting in data
	corruption.  Applications may be affected.
action: Restore the file in question if possible.  Otherwise restore the
	entire pool from backup.
   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-8A
  scan: scrub repaired 24K in 00:00:01 with 1 errors on Tue Jan 16 14:06:23 2024
config:

	NAME        STATE     READ WRITE CKSUM
	iron5       DEGRADED     0     0     0
	  raidz2-1  DEGRADED     0     0     0
	    L2      FAULTED      0     0     0  too many errors
	  raidz2-5  ONLINE       1     0     0
	    L23     ONLINE       1     0     0
	    L24     ONLINE       1     0     0
	    L37     ONLINE       1     0     0
	  raidz2-6  DEGRADED     0     0     0
	    L67     FAULTED      0     0     0  too many errors

errors: 1 data errors, use '-v' for a list

- Vdev missing
	[root@iron5:zfs2.2]# ./zpool status -e
		pool: iron5
	 state: DEGRADED
	status: One or more devices could not be used because the label is missing or
		invalid.  Sufficient replicas exist for the pool to continue
		functioning in a degraded state.
	action: Replace the device using 'zpool replace'.
	   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-4J
	  scan: scrub repaired 0B in 00:00:01 with 0 errors on Thu Jan 11 14:42:30 2024
	config:

		NAME        STATE     READ WRITE CKSUM
		iron5       DEGRADED     0     0     0
		  raidz2-6  DEGRADED     0     0     0
		    L67     UNAVAIL      3     1     0

Signed-off-by: Cameron Harr <[email protected]>

Author: cmharr