[WAYP-2783] Add support for a "hidden" tag for api-docs (#2565)

This allows us to tag RPCs as `hidden` to prevent them appearing in
API docs.

Looks like this in practice:

    rpc UI_LoadProductBanner(UI.LoadProductBannerRequest) returns (UI.LoadProductBannerResponse) {
      option (google.api.http) = {
        get: "/waypoint/2023-08-18/namespace/{namespace.id}/ui/product-banner"
      };
      option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
        tags: ["WaypointService", "hidden"]
      };
    }

src/views/open-api-docs-view/utils/get-operation-props.ts

@@ -51,6 +51,10 @@ export async function getOperationProps(
 				continue
 			}
 
+			if (operation.tags?.includes('hidden')) {
+				continue
+			}
+
 			// Create a slug for this operation
 			const operationSlug = slugify(operation.operationId)