Automate updating of pinned dependencies

[mthalman]

There are several tool dependencies that the VMR has which use pinned versions to avoid being broken mid-release by an update:

• Pin OmniSharp version used for testing installer#17074
• Pin scancode version installer#17602

There should be an automated system for updating these to the latest version. I propose that this be done as part of the release pipeline when it generates a PR with the post-release changes (e.g. dotnet/installer#17349).

[MichaelSimons]

[Triage] A possibility on where to track the versions would be the VMR's versions.props file.

[MichaelSimons]

[Triage] This is a good candidate to consider backporting.