Refactor sample generator in mgmt

[ArcturusZhang]

Fixes #5079

Description

A thorough refactor on how the samples are written in mgmt plane.

• Move the part that converts an example value into expression to the common place, so that the mgmt sample generator could call it as well
• Sample generation is no longer a standalone target. It is now part of the target of generating the source code.
• MgmtTestConfiguration remains. We will refactor those parts in later PRs, including introducing similar configurations to typespec input

About changes in regen PR:
We do have quite a lot of changes in the regen PR, because now to generate the content of the sample, we are reusing the code written for DPG's sample a few months ago, which introduces quite a few style changes, such as, previously we might have:

VirtualMachineData data = new VirtualMachineData()
{
	Location = AzureLocation.WestUS
};

now we might have:

VirtualMachineData data = new VirtualMachineData
{
	Location = AzureLocation.WestUS
};

Also because of now sample generation is not in a standalone target, we have quite a few order changes in those generated methods.
To summary, the majority of those massive changes in the regen PR come from the style change, or ordering change.

Checklist

To ensure a quick review and merge, please ensure:

• The PR has a understandable title and description explaining the why and what.
• The PR is opened in draft if not ready for review yet.
  • If opened in draft, please allocate sufficient time (24 hours) after moving out of draft for review
• The branch is recent enough to not have merge conflicts upon creation.

Ready to Land?

• Build is completely green
  • Submissions with test failures require tracking issue and approval of a CODEOWNER
• At least one +1 review by a CODEOWNER
• All -1 reviews are confirmed resolved by the reviewer
  • Override/Marking reviews stale must be discussed with CODEOWNERS first