Infrastructure: Consider deploying vcpkg dependencies on the VMs so that they need not be built during CI or PR test

[BillyONeal]

This would involve changing provision-image.ps1 to check out a vcpkg instance and install our prerequisites on the C:\ drive, then change our build YAML scripts to reference that installed vcpkg rather than initializing our submodule.

[StephanTLavavej]

#2151 has removed vcpkg so there's nothing to do here.