* nxos_vlan: fix broken purge behavior (issue #57101)
Symptoms/Analysis:
- `nxos_vlan` `purge: true` would fail when `purge` was trying to delete all unspecified vlans, including vlan 1.
- `nxos` devices do not allow removing vlan 1 and raise a cli exception error
- Previous fix#55144 caused a side effect when `purge` was used: vlan changes specified by `aggregate` were ignored; e.g.
- vlan 4 is not present; playbook specifies `aggregate: { vlan: 4 }, purge: true`
- results in proper purging but vlan 4 is not created
Solutions:
- ignore vlan 1 when purging
- remove the `not purge` check from state present logic
Added additional unit tests and integration tests.
Tested against all regression platforms.
* PEP fixes
* Add agg_show_vlan_brief.txt fixture
* Add warning for removing vlan 1
* change method name check
