Standardize label validation in JSON schemas to conform with GCP platform limits (#4021)

Co-authored-by: Ludovico Magnocavallo <ludomagno@google.com>

modules/net-vpc/schemas/internal-range.schema.json

@@ -19,8 +19,12 @@
     "labels": {
       "type": "object",
       "description": "User-defined labels.",
-      "additionalProperties": {
-        "type": "string"
+      "additionalProperties": false,
+      "patternProperties": {
+        "^[a-z][a-z0-9_-]{0,62}$": {
+          "type": "string",
+          "pattern": "^[a-z0-9_-]{0,63}$"
+        }
       }
     },
     "ip_cidr_range": {

modules/net-vpc/schemas/internal-range.schema.md

@@ -9,7 +9,9 @@
 - **name**: *string*
 - **description**: *string*
 - **labels**: *object*
-  <br>*additional properties: string*
+  <br>*additional properties: false*
+  - **`^[a-z][a-z0-9_-]{0,62}$`**: *string*
+    <br>*pattern: ^[a-z0-9_-]{0,63}$*
 - **ip_cidr_range**: *string*
 - ⁺**usage**: *string*
   <br>*enum: ['FOR_VPC', 'EXTERNAL_TO_VPC', 'FOR_MIGRATION']*