* Adds scripts to generate scale sets for testing Linux.
* Note workaround for https://github.com/microsoft/azure-pipelines-agent/pull/2929
* Switches Windows validation to 'Spot' VMs.
* Opens the git port 9418.
* Removes provisioning of the no longer used 'logs' file share.
* Changes Azure region to 'westus2', which is cheaper.
* Adds +x to all the scripts in scripts/azure-pipelines.
* Use 'xml-results' for all platforms instead of 'raw xml results' on Windows.
Included is a script that sets up all vcpkg's Azure infrastructure for Windows PR tests, and several updates to baselines. The baseline updates are generally caused by an updated copy of the MSVC++ compiler caused by updating the VMs, but some are caused by missed failures only detected now because this did a cleared out archives directory first.
Some of the build infrastructure isn't what I'd call 'pretty' (e.g. we're split into more scripts and such than I'd like) but this mirrors how our existing PR system works.
It is expected that the existing vcpkg Windows PR system will hate these baseline updates so we'll need to merge this, then remove that (duplicate) workflow immediately afterwards, then delete all the Windows VMs powering the old infrastructure.
