zpool/zfs: Add '-a|--all' option to scrub, trim, initialize

Add support for the '-a | --all' option to perform trim,
scrub, and initialize operations on all pools.
Previously, specifying a pool name was mandatory for
these operations. With this enhancement, users can now
execute these operations across all pools at once,
without needing to manually iterate over each pool
from the command line.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Akash B <akash-b@hpe.com>
Closes #17524

man/man8/zpool-initialize.8

@@ -26,6 +26,7 @@
 .\" Copyright (c) 2018 George Melikov. All Rights Reserved.
 .\" Copyright 2017 Nexenta Systems, Inc.
 .\" Copyright (c) 2017 Open-E, Inc. All Rights Reserved.
+.\" Copyright (c) 2025 Hewlett Packard Enterprise Development LP.
 .\"
 .Dd May 27, 2021
 .Dt ZPOOL-INITIALIZE 8
@@ -39,7 +40,7 @@
 .Cm initialize
 .Op Fl c Ns | Ns Fl s | Ns Fl u
 .Op Fl w
-.Ar pool
+.Fl a Ns | Ns Ar pool
 .Oo Ar device Oc Ns …
 .
 .Sh DESCRIPTION
@@ -48,6 +49,10 @@ devices, or all eligible devices in the pool if no individual devices are
 specified.
 Only leaf data or log devices may be initialized.
 .Bl -tag -width Ds
+.It Fl a , -all
+Begin, cancel, suspend initializing on
+all
+pools.
 .It Fl c , -cancel
 Cancel initializing on the specified devices, or all eligible devices if none
 are specified.