Add API tests for subnet pool prefix operations

This introduces API tests for the subnetpool_prefix_ops
extension. These tests assert proper addition and removal of
prefixes against subnet pools under the various scenarios that
are supported.

Related-Bug: #1792901
Depends-On: https://review.opendev.org/#/c/648197/
Change-Id: I51564669fc1113556b0927296fa9dd2a8806bce8
diff --git a/.zuul.yaml b/.zuul.yaml
index fbfcad6..dbae6e4 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -74,6 +74,7 @@
         - standard-attr-tag
         - standard-attr-timestamp
         - subnet_allocation
+        - subnetpool-prefix-ops
         - trunk
         - trunk-details
         - uplink-status-propagation