Ensure that version in vcpkg.json and AzureVcpkg.cmake are the same

[danieljurek]

Dependabot opens updates to vcpkg.json but has no way of updating AzureVcpkg.cmake. When the two values diverge it can result in bad build behavior.

Two possible fixes:

• Have AzureVcpkg.cmake read the value from vcpkg.json (requires upgrading minimum cmake version to 3.19) OR
• Have some kind of additional check that fails if the values in those files differ OR
• A GitHub Action (or some kind of automation) that updates PRs opened by dependabot when it makes sense to do so