[YANG] add yang model for MUX_LINKMGR|MUXLOGGER (#15884) (#16021)

Add yang model for MUX_LINKMGR|MUXLOGGER.

Co-authored-by: Jing Zhang <zhangjing@microsoft.com>

src/sonic-yang-models/doc/Configuration.md

@@ -1164,6 +1164,9 @@ The **MUX_LINKMGR** table is used for dualtor device configuration.
             "use_well_known_mac": "enabled",
             "src_mac": "ToRMac",
             "interval_pck_loss_count_update": "3"
+        },
+        "MUXLOGGER": {
+            "log_verbosity": "debug"
         }
     }
 }

src/sonic-yang-models/tests/files/sample_config_db.json

@@ -1837,6 +1837,9 @@
                 "use_well_known_mac": "enabled",
                 "src_mac": "ToRMac",
                 "interval_pck_loss_count_update": "3"
+            },
+            "MUXLOGGER": {
+                "log_verbosity": "debug"
             }
         },
 

src/sonic-yang-models/tests/yang_model_tests/tests/mux-linkmgr.json

@@ -4,5 +4,8 @@
     },
     "MUX_LINKMGR_LINK_PROBER_CHANGE_MAC_ADDR": {
         "desc": "Use well-known mac and vlan mac as dst/src in linkmgrd link prober. "
+    },
+    "MUX_LINKMGR_MUXLOGGER_CHANGE_VERBOSITY_LEVEL": {
+        "desc": "Consume verbosity level config changes. "
     }
 }

src/sonic-yang-models/tests/yang_model_tests/tests_config/mux-linkmgr.json

@@ -22,5 +22,15 @@
                     }
             }
         }
+    },
+    "MUX_LINKMGR_MUXLOGGER_CHANGE_VERBOSITY_LEVEL": {
+        "sonic-mux-linkmgr:sonic-mux-linkmgr": {
+            "sonic-mux-linkmgr:MUX_LINKMGR": {
+                "sonic-mux-linkmgr:MUXLOGGER": 
+                    {
+                        "log_verbosity": "debug"
+                    }
+            }
+        }
     }
 }

src/sonic-yang-models/yang-models/sonic-mux-linkmgr.yang

@@ -83,6 +83,21 @@ module sonic-mux-linkmgr {
                     description "The frequency of streaming ICMP heartbeat loss data to telemetry. ";
                 }
             }
+
+            container MUXLOGGER {
+
+                leaf log_verbosity {
+                    type enumeration {
+                        enum trace;
+                        enum debug;
+                        enum info;
+                        enum error;
+                        enum fatal;
+                    }
+
+                    description "Linkmgrd log verbosity level. ";
+                }
+            }
         }
     }
 }