Fix subnet schema in net-vpc module & hybrid subnets example implementation (#2958)

* Fixed subnet schema by adding "allow_subnet_cidr_routes_overlap" field

* Implemented hybrid subnets code example and test code

modules/net-vpc/README.md

@@ -95,10 +95,17 @@ module "vpc" {
         flow_sampling        = 0.5
         aggregation_interval = "INTERVAL_10_MIN"
       }
+    },
+    # hybrid subnet
+    {
+      name                             = "hybrid"
+      region                           = "europe-west1"
+      ip_cidr_range                    = "10.0.4.0/24"
+      allow_subnet_cidr_routes_overlap = true
     }
   ]
 }
-# tftest modules=1 resources=7 inventory=subnet-options.yaml e2e
+# tftest modules=1 resources=8 inventory=subnet-options.yaml e2e
 ```
 
 ### Subnet IAM

modules/net-vpc/schemas/subnet.schema.json

@@ -17,6 +17,9 @@
     "enable_private_access": {
       "type": "boolean"
     },
+    "allow_subnet_cidr_routes_overlap": {
+      "type": "boolean"
+    },
     "flow_logs_config": {
       "type": "object",
       "additionalProperties": false,