Add build checks in Azure Pipelines

[FISHMANPET]

Since us Azure Pipelines people keep introducing changes that break Pipelines for other people, I think it would be useful if there were build checks that ran in Azure Pipelines for the 3 conditions, YAML, Classic Build, and Classic Release. It could be as simple as just running Set-BuildEnvironment because the bugs we're fixing are the result of that breaking, but it would probably make sense to also run the full test suite while we're in there.

I'll volunteer to set those up (Azure Devops is free for open source projects) but I'd need to work with you @RamblingCookieMonster to get it linked into this repo