chore(oapi): move global inisight schema to separate object (#12456)

## Motivation

So it's properly merged in parent object. Otherwise we end up with both
`properties` and `allOf` on the same level which doesn't play nicely
with parent project validator.

<!-- Why are we doing this change -->

## Implementation information

Move to separate object.

<!-- Explain how this was done and potentially alternatives considered
and discarded -->

## Supporting documentation

<!-- Is there a MADR? An Issue? A related PR? -->

xrel kumahq/ci-tools#59

<!--
> Changelog: skip
-->
<!--
Uncomment the above section to explicitly set a [`> Changelog:` entry
here](https://github.com/kumahq/kuma/blob/master/CONTRIBUTING.md#submitting-a-patch)?
-->

---------

Signed-off-by: slonka <[email protected]>

api/openapi/specs/api.yaml

@@ -390,7 +390,7 @@ components:
           type: integer
           description: Number of meshes
           example: 3
-    GlobalInsight:
+    schemas-GlobalInsight:
       type: object
       title: GlobalInsight
       description: Global Insight contains statistics for all main resources
@@ -433,6 +433,9 @@ components:
           additionalProperties:
             $ref: '#/components/schemas/ResourceStats'
           description: A map of resource names to their corresponding statistics
+    GlobalInsight:
+      allOf:
+        - $ref: '#/components/schemas/schemas-GlobalInsight'
   responses:
     IndexResponse:
       description: A response for the index endpoint

docs/generated/openapi.yaml

@@ -2448,7 +2448,7 @@ components:
           type: integer
           description: Number of meshes
           example: 3
-    GlobalInsight:
+    schemas-GlobalInsight:
       type: object
       title: GlobalInsight
       description: Global Insight contains statistics for all main resources
@@ -2491,6 +2491,9 @@ components:
           additionalProperties:
             $ref: '#/components/schemas/ResourceStats'
           description: A map of resource names to their corresponding statistics
+    GlobalInsight:
+      allOf:
+        - $ref: '#/components/schemas/schemas-GlobalInsight'
     PolicyDescription:
       type: object
       required: