feat: Add VLAN management for network_interface object

[KTokarze]

This pull request introduces a new set of VLAN management functionalities for Linux network interfaces in the LinuxVLAN class and corresponding unit tests to ensure their correctness. The most important changes include adding methods for VLAN operations, integrating a custom debug logging level, and implementing comprehensive unit tests for these features.

New VLAN Management Features:

• Added get_vlan_ids, get_vlan_id, add_vlan, and remove_vlan methods to the LinuxVLAN class for managing VLANs on Linux network interfaces. These methods use terminal commands to retrieve, add, or remove VLANs and include logging at a custom debug level (MFD_DEBUG). ([mfd_network_adapter/network_interface/feature/vlan/linux.pyR18-R105](https://github.com/intel/mfd-network-adapter/pull/6/files#diff-5d4dc140cc93d93c5a6ae3daf2804afa691e7d49f21d27ddf668708b1c67d25fR18-R105))

Logging Enhancements:

• Imported and integrated MFD_DEBUG logging level from mfd_common_libs.log_levels to provide detailed debug logs for VLAN operations. ([mfd_network_adapter/network_interface/feature/vlan/linux.pyR8-R9](https://github.com/intel/mfd-network-adapter/pull/6/files#diff-5d4dc140cc93d93c5a6ae3daf2804afa691e7d49f21d27ddf668708b1c67d25fR8-R9))

Unit Tests for VLAN Features:

• Created a new test suite in tests/unit/test_mfd_network_adapter/test_network_interface/test_feature/test_vlan/test_vlan_linux.py to validate the functionality of VLAN methods. Tests cover scenarios such as adding, removing, and retrieving VLANs, including edge cases like no VLANs being present. ([tests/unit/test_mfd_network_adapter/test_network_interface/test_feature/test_vlan/test_vlan_linux.pyR1-R117](https://github.com/intel/mfd-network-adapter/pull/6/files#diff-39cadbe91660cc9cf2b65aa52068fd76cb7d9bdc83c8ff9689261b9b83bfc17dR1-R117))**

[Copilot]

Pull Request Overview

This pull request introduces comprehensive VLAN management functionality for Linux network interfaces by implementing the LinuxVLAN class with methods for creating, removing, and querying VLANs. The changes include adding four core VLAN operations, integrating custom debug logging, and providing extensive unit test coverage.

Key changes:

• Implementation of VLAN management methods (get_vlan_ids, get_vlan_id, add_vlan, remove_vlan) in the LinuxVLAN class
• Addition of new VLAN-specific exceptions (VlanAlreadyExistsException, VlanNotFoundException)
• Comprehensive unit test suite covering all VLAN operations and edge cases

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
mfd_network_adapter/network_interface/feature/vlan/linux.py	Core VLAN management implementation with methods for adding, removing, and querying VLANs
mfd_network_adapter/exceptions.py	Addition of VlanAlreadyExistsException for VLAN conflict handling
tests/unit/test_mfd_network_adapter/test_network_interface/test_feature/test_vlan/test_vlan_linux.py	Complete unit test suite validating VLAN functionality and error conditions
README.md	Documentation updates describing the new VLAN management API

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