[yang] Adding sonic-bgp-monitor to setup.py (#9877)

#### Why I did it
Include sonic-bgp-monitor to setup.py so it gets included in /usr/local/yang-models when installing the package

#### How I did it

#### How to verify it
install the package

#### Which release branch to backport (provide reason below if selected)

<!--
- Note we only backport fixes to a release branch, *not* features!
- Please also provide a reason for the backporting below.
- e.g.
- [x] 202006
-->

- [ ] 201811
- [ ] 201911
- [ ] 202006
- [ ] 202012
- [ ] 202106

#### Description for the changelog
<!--
Write a short (one line) summary that describes the changes in this
pull request for inclusion in the changelog:
-->


#### A picture of a cute animal (not mandatory but encouraged)

src/sonic-yang-models/setup.py

@@ -81,6 +81,7 @@ setup(
                          './yang-models/sonic-auto_techsupport.yang',
                          './yang-models/sonic-bgp-common.yang',
                          './yang-models/sonic-bgp-global.yang',
+                         './yang-models/sonic-bgp-monitor.yang',
                          './yang-models/sonic-bgp-neighbor.yang',
                          './yang-models/sonic-bgp-peergroup.yang',
                          './yang-models/sonic-breakout_cfg.yang',
@@ -145,6 +146,7 @@ setup(
         ('cvlyang-models', ['./cvlyang-models/sonic-acl.yang',
                          './cvlyang-models/sonic-bgp-common.yang',
                          './cvlyang-models/sonic-bgp-global.yang',
+                         './cvlyang-models/sonic-bgp-monitor.yang',
                          './cvlyang-models/sonic-bgp-neighbor.yang',
                          './cvlyang-models/sonic-bgp-peergroup.yang',
                          './cvlyang-models/sonic-breakout_cfg.yang',

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

@@ -1147,6 +1147,18 @@
             "default|ipv4_unicast|21.0.0.0/8": {
             }
         },
+        "BGP_MONITORS": {
+            "5.6.7.8": {
+                "admin_status": "up",
+                "asn": "65000",
+                "holdtime": "180",
+                "keepalive": "60",
+                "local_addr": "10.0.0.11",
+                "name": "BGPMonitor",
+                "nhopself": "0",
+                "rrclient": "0"
+            }
+        },
         "BGP_NEIGHBOR": {
             "10.0.0.1": {
                 "asn": "65200",