[dotnet] Add Virtual Authenticator support

[pujagani]

Thanks for contributing to Selenium!
A PR well described will help maintainers to quickly review and merge it

Before submitting your PR, please check our contributing guidelines.
Avoid large PRs, help reviewers by making them as simple and short as possible.

Description

Related to #10541

Motivation and Context

Add Virtual Authenticator support for Dotnet bindings.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[titusfortner]

@pujagani I pulled this code and validated the tests. The one nitpick is that the convention in this project is to put

get { return "whatever"; }

all on one line unless there is a multi-line return, but the code works.

More importantly, I made some other updates that means this PR needs to be rebased off latest.