[PBH] CLI for Policy Based Hashing (sonic-net#1701)

- What I did
Created click CLI plugins for PBH feature

- How I did it
The CLI plugins were auto-generated (by using the sonic-cli-gen) for show and config CLI groups, then manually those were manually edited to meet PBH the CLI requirements according to the PBH HLD

- How to verify it
Added the UT

clear/main.py

@@ -2,11 +2,12 @@
 import os
 import subprocess
 import sys
-
 import click
+import utilities_common.cli as clicommon
+import json
 
 from utilities_common import util_base
-
+from show.plugins.pbh import read_pbh_counters
 from . import plugins
 
 
@@ -449,6 +450,31 @@ def translations():
     cmd = "natclear -t"
     run_command(cmd)
 
+# 'pbh' group ("clear pbh ...")
+@cli.group(cls=AliasedGroup)
+def pbh():
+    """ Clear the PBH info """
+    pass
+
+# 'statistics' subcommand ("clear pbh statistics")
+@pbh.command()
+@clicommon.pass_db
+def statistics(db):
+    """ Clear PBH counters
+        clear counters -- write current counters to file in /tmp
+    """
+
+    pbh_rules = db.cfgdb.get_table("PBH_RULE")
+    pbh_counters = read_pbh_counters(pbh_rules)
+
+    try:
+        with open('/tmp/.pbh_counters.txt', 'w') as fp:
+            json.dump(remap_keys(pbh_counters), fp)
+    except IOError as err:
+        pass
+
+def remap_keys(dict):
+    return [{'key': k, 'value': v} for k, v in dict.items()]
 
 # Load plugins and register them
 helper = util_base.UtilHelper()