Adds the bigip_gtm_server module (#34513)

This module can be used to create GTM servers (not to be confused with
GTM virtual servers) on a BIGIP. GTM servers are a component of the
datacenter, and GTM virtual servers are their members.

test/units/modules/network/f5/fixtures/load_gtm_server_1.json

@@ -0,0 +1,68 @@
+{
+    "kind": "tm:gtm:server:serverstate",
+    "name": "baz",
+    "partition": "Common",
+    "fullPath": "/Common/baz",
+    "generation": 270,
+    "selfLink": "https://localhost/mgmt/tm/gtm/server/~Common~baz?ver=13.0.0",
+    "datacenter": "/Common/foo",
+    "datacenterReference": {
+        "link": "https://localhost/mgmt/tm/gtm/datacenter/~Common~foo?ver=13.0.0"
+    },
+    "enabled": true,
+    "exposeRouteDomains": "no",
+    "iqAllowPath": "yes",
+    "iqAllowServiceCheck": "yes",
+    "iqAllowSnmp": "yes",
+    "limitCpuUsage": 0,
+    "limitCpuUsageStatus": "disabled",
+    "limitMaxBps": 0,
+    "limitMaxBpsStatus": "disabled",
+    "limitMaxConnections": 0,
+    "limitMaxConnectionsStatus": "disabled",
+    "limitMaxPps": 0,
+    "limitMaxPpsStatus": "disabled",
+    "limitMemAvail": 0,
+    "limitMemAvailStatus": "disabled",
+    "linkDiscovery": "disabled",
+    "monitor": "/Common/bigip ",
+    "proberFallback": "inherit",
+    "proberPreference": "inherit",
+    "product": "bigip",
+    "virtualServerDiscovery": "disabled",
+    "addresses": [
+        {
+            "name": "1.1.1.1",
+            "deviceName": "bigip1",
+            "translation": "10.10.10.10"
+        },
+        {
+            "name": "2.2.2.2",
+            "deviceName": "bigip2",
+            "translation": "20.20.20.20"
+        },
+        {
+            "name": "3.3.3.3",
+            "deviceName": "bigip2",
+            "translation": "20.20.20.20"
+        },
+        {
+            "name": "4.4.4.4",
+            "deviceName": "bigip3",
+            "translation": "none"
+        },
+        {
+            "name": "5.5.5.5",
+            "deviceName": "bigip3",
+            "translation": "none"
+        }
+    ],
+    "devicesReference": {
+        "link": "https://localhost/mgmt/tm/gtm/server/~Common~baz/devices?ver=13.0.0",
+        "isSubcollection": true
+    },
+    "virtualServersReference": {
+        "link": "https://localhost/mgmt/tm/gtm/server/~Common~baz/virtual-servers?ver=13.0.0",
+        "isSubcollection": true
+    }
+}