[http-client-csharp] add regen preview local validation script

[jorgerangel-msft]

This PR adds a new regen preview developer script to aid in testing and validating changes made to the generator. It allows regenerating azure libraries locally using the local artifacts of the generator, helping to see what the regenerated code will look like with the applied changes.

contributes to: Azure/azure-sdk-for-net#52234

example run:

[github-actions]

No changes needing a change description found.

[azure-sdk]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

[JoshLove-msft]

I tested this locally making a change in CodeWriter to the auto-generated string and ran for all libraries, but only Azure.AI.Projects showed any diffs.

[jorgerangel-msft]

I tested this locally making a change in CodeWriter to the auto-generated string and ran for all libraries, but only Azure.AI.Projects showed any diffs.

Strange. I tested this on 2 separate machines and it worked fine. I'll need to debug to see why that would happen.

[JoshLove-msft]

I tested this locally making a change in CodeWriter to the auto-generated string and ran for all libraries, but only Azure.AI.Projects showed any diffs.

Strange. I tested this on 2 separate machines and it worked fine. I'll need to debug to see why that would happen.

Hmm let me try again.

[JoshLove-msft]

I tested this locally making a change in CodeWriter to the auto-generated string and ran for all libraries, but only Azure.AI.Projects showed any diffs.

Strange. I tested this on 2 separate machines and it worked fine. I'll need to debug to see why that would happen.

Hmm let me try again.

Nevermind - I must have been looking at an out of sync diff. It is working as expected.