Add upcoming renaming notice for arc_summary and arcstat

They will become zarcsummary and zarcstat in 2.4.0.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Shengqi Chen <harry-chen@outlook.com>
Closes #16357
Closes #17695

cmd/arc_summary

@@ -1021,6 +1021,13 @@ def main():
     treated separately because they come with their own call.
     """
 
+    # notify user for upcoming renaming in 2.4.0
+    abs_path = os.path.abspath(sys.argv[0].strip())
+    script_name = os.path.basename(abs_path)
+    if script_name != "zarcsummary":
+        sys.stderr.write("Note: this script will be renamed to zarcsummary in ")
+        sys.stderr.write("zfs 2.4.0. Please migrate ASAP.\n")
+
     kstats = get_kstats()
 
     if ARGS.graph:

cmd/arcstat.in

@@ -56,6 +56,7 @@ import time
 import getopt
 import re
 import copy
+import os
 
 from signal import signal, SIGINT, SIGWINCH, SIG_DFL
 
@@ -766,6 +767,14 @@ def calculate():
 
 
 def main():
+
+    # notify user for upcoming renaming in 2.4.0
+    abs_path = os.path.abspath(sys.argv[0].strip())
+    script_name = os.path.basename(abs_path)
+    if script_name != "zarcstat":
+        sys.stderr.write("Note: this script will be renamed to zarcstat in ")
+        sys.stderr.write("zfs 2.4.0. Please migrate ASAP.\n")
+
     global sint
     global count
     global hdr_intr

man/man1/arcstat.1

@@ -20,6 +20,8 @@
 .Sh NAME
 .Nm arcstat
 .Nd report ZFS ARC and L2ARC statistics
+.Sh NOTICE
+It will be renamed to zarcstat in zfs 2.4.0. Please migrate ASAP.
 .Sh SYNOPSIS
 .Nm
 .Op Fl havxp