WIP: Publsh to nuget.org

[szh]

Desired Outcome

Add a build step to publish the .NET SDK to NuGet.

Implemented Changes

Describe how the desired outcome above has been achieved with this PR. In
particular, consider:

• What's changed? Why were these changes made?
• How should the reviewer approach this PR, especially if manual tests are required?
• Are there relevant screenshots you can add to the PR description?

Connected Issue/Story

CyberArk internal issue ID: ONYX-18165

Definition of Done

At least 1 todo must be completed in the sections below for the PR to be
merged.

Changelog

• The CHANGELOG has been updated, or
• This PR does not include user-facing changes and doesn't require a
  CHANGELOG update

Test coverage

• This PR includes new unit and integration tests to go with the code
  changes, or
• The changes in this PR do not require tests

Documentation

• Docs (e.g. READMEs) were updated in this PR
• A follow-up issue to update official docs has been filed here: [insert issue ID]
• This PR does not require updating any documentation

Behavior

• This PR changes product behavior and has been reviewed by a PO, or
• These changes are part of a larger initiative that will be reviewed later, or
• No behavior was changed with this PR

Security

• Security architect has reviewed the changes in this PR,
• These changes are part of a larger initiative with a separate security review, or
• There are no security aspects to these changes

[jtuttle]

@LukaszStrz FYI. Not sure if Synchronizer has gotten super involved in this repo yet, but we had a Focus Friday project to push to NuGet that Shlomo picked up.

[szh]

Currently the thing holding this up is that there's already a version published on Nuget by a third party. @ismarc is going to work on contacting Microsoft to take ownership of the package.