Integrate the iOS test runner into the build

[steveisok]

We want to make the mobile testing experience as similar as possible, so the end goal should be:

build.sh/cmd -os iOS -arch <x86/arm/arm64> -Subset mono+libs+libs.test -test -c Release

Within that, we need to accomplish (feel free to add others):

• Migrate existing props and targets into the libraries test build flow
• If not already there, add target to redirect publish to use the in tree runtime pack folder
• Modify build to use dotnet publish for each test suite. If 1 app per suite is not appropriate locally, adjust to something more acceptable.
• Enable property to specify a provisioning profile (device test runs)

Tagging subscribers to this area: @directhex
Notify danmosemsft if you want to be subscribed.