Change zpool email notifications to display the actual pool name instead of the pool GUID

[WRMSRwasTaken]

Motivation and Context

The current mail for a device / pool state change is printing out the pool GUID instead of the pool name in the email being sent. As a system administrator, I'd like to get a direct idea what is going on, and because I have multiple pools in my system, I don't know which pool just had the said event. (who memorizes pool GUIDs?)
Email notifications for finishing a pool resilver already do this.

Description

Changing zed's statechange-notify.sh ZEVENT_POOL_GUID variable to ZEVENT_POOL.
If people like to have the pool GUID aswell, it could be added aswell alongside the pool name. Or make it even configurable, like zed's syslog output (ZED_SYSLOG_DISPLAY_GUIDS).

How Has This Been Tested?

I applied the patch on one of my machines known to have not 100% reliable disks (with data I have backup-ed elsewhere) and let it run:

The number of I/O errors associated with a ZFS device exceeded
acceptable levels. ZFS has marked the device as faulted.

 impact: Fault tolerance of the pool may be compromised.
    eid: 3624
  class: statechange
  state: FAULTED
   host: <redacted>
   time: 2022-12-08 22:27:18+0100
  vpath: /dev/disk/by-partuuid/e32fbbe6-38e7-c94e-a655-6e3c480fb25a
  vguid: 0xF7D486597705238B
   pool: hdd2

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

Makes sense to me. Even though the pool name may not be unique, it is the kind of thing you'd want to see in a human friendly notification.

[allanjude]

Might we want to keep the GUID in the email as well though?

[ryao]

Might we want to keep the GUID in the email as well though?

I am inclined to think that we should include the GUID too just in case.