Initial vcpkg updater

[JamieMagee]

What are you trying to accomplish?

Add support for updating VCPKG projects.

Currently supports updating the builtin-baseline property in the vcpkg.json file.

Currently does not support updating the default-registry property in the vcpkg-configuration.json file or the registries property in the vcpkg-configuration.json file.

See JamieMagee/dependabot-vcpkg for examples.

Anything you want to highlight for special attention from reviewers?

Related:

• add vcpkg ecosystem #7644
• Add vcpkg support cli#462
• Add vcpkg smoke tests smoke-tests#300
• Add vcpkg ecosystem support github/dependabot-action#1503

How will you know you've accomplished your goal?

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

[brettfo]

Discussed offline some internal-only changes that will need to accompany this.