feat: install LTS kernel for Ubuntu when available

[anujmaheshwari1]

What type of PR is this?
This PR adds functionality to install LTS kernel for Ubuntu VHDs, when available. It also adds VHD content tests to ensure the right LTS kernel is installed on the VHD depending on the Ubuntu version.

Successful VHD build: https://msazure.visualstudio.com/CloudNativeCompute/_build/results?buildId=115093843&view=results

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Special notes for your reviewer:

Release note:

none

[zachary-bailey]

Why do we not want the 6.8 kernel for 22.04?

This table shows 6.8 is LTS for 22.04, but it is the HWE variant. Is that why?

Kernel Release Cycle Docs

UPDATE: Ahh, it seems there is no azure-specific 6.8 for 22.04?

[anujmaheshwari1]

Why do we not want the 6.8 kernel for 22.04?

This table shows 6.8 is LTS for 22.04, but it is the HWE variant. Is that why?

Kernel Release Cycle Docs

UPDATE: Ahh, it seems there is no azure-specific 6.8 for 22.04?

correct Zach, we dont want the HWE variant to determine the LTS kernel to install.