feat: add Catalyst Center dynamic inventory plugin

Add cisco.catalystcenter.catalystcenter inventory plugin that queries
Catalyst Center for managed devices and builds Ansible inventory with
site hierarchy groups, device role/family groups, tag groups, and full
Constructable support (keyed_groups, compose, conditional groups).

Key features:
- Uses catalystcentersdk (same SDK as the collection modules)
- Pagination for large deployments (500+ devices)
- Caching via standard Ansible cache framework
- Auto-sets ansible_network_os for IOS-XE and NX-OS (FQCNs)
- AP filtering (excluded by default)
- Environment variable fallback (CATALYSTCENTER_*)

Based on jandiorio/ansible-dnac-inventory-plugin, modernized with
BaseInventoryPlugin + Constructable + Cacheable pattern.

Includes 29 unit tests and integration test target.

Author: Test User

changelogs/fragments/inventory-plugin.yml

@@ -0,0 +1,6 @@
+---
+minor_changes:
+  - "Added ``cisco.catalystcenter.catalystcenter`` dynamic inventory plugin for building Ansible inventory from Catalyst Center managed devices."
+  - "Inventory plugin supports site hierarchy grouping, device role and family groups, tag-based groups, and full Constructable features (keyed_groups, compose, groups)."
+  - "Inventory plugin supports caching via the standard Ansible cache framework."
+  - "Inventory plugin auto-sets ``ansible_network_os`` and ``ansible_connection`` for IOS-XE and NX-OS devices using FQCNs."

meta/runtime.yml

@@ -1,2 +1,6 @@
 ---
 requires_ansible: '>=2.16.0'
+plugin_routing:
+  inventory:
+    catalystcenter:
+      redirect: cisco.catalystcenter.catalystcenter