e2e-tests (4/4): Add e2e testdata fixtures for all resources types

[nikatza]

This PR adds testdata fixtures for all 23 resource types, enabling comprehensive e2e testing of the network operator. Each test validates that the operator correctly translates Kubernetes resources into the appropriate device configuration via gNMI.

What's New

NX-OS Resource Tests (21 tests)

Each test is a separate txtar file:

Basic Configuration Resources:

• banner.txt - System banner messages
• dns.txt - DNS server configuration
• ntp.txt - NTP server and authentication
• lldp.txt - Link Layer Discovery Protocol
• snmp.txt - SNMP server and community configuration
• syslog.txt - Syslog server configuration

Network Resources:

• vrf.txt - Virtual Routing and Forwarding instances
• routedvlan.txt - L3 VLAN interfaces
• subinterface.txt - 802.1Q subinterfaces

Routing Resources:

• routingpolicy_prefixset.txt - Route filtering and policy
• bgp_bgppeer.txt - Border Gateway Protocol
• ospf.txt - Open Shortest Path First
• pim.txt - Protocol Independent Multicast
• isis.txt - Intermediate System to Intermediate System

EVPN/VXLAN Resources:

• nve.txt - Network Virtualization Edge (VXLAN)
• evpninstance.txt - EVPN instance configuration
• vpcdomain.txt - Virtual Port Channel domain

Security & Services:

• acl.txt - ACL rules and entries
• dhcprelay.txt - DHCP relay configuration
• managementaccess.txt - Management interface ACLs

OpenConfig Provider Test (1 test)

• interface.txt - Demonstrates multi-provider support using OpenConfig models

Test Format

All tests use the txtar format. Each .txt file contains:

• Kubernetes resource manifests (Device, Interface, VRF, etc.)
• Expected gNMI configuration updates
• Test metadata (provider, description)