Better async support

[dharmaturtle]

No description provided.

[github-actions]

Pull Request Test Coverage Report for Build 5431066058

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 89.13%

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Totals
Change from base Build 5406784932:	0.0%
Covered Lines:	197
Relevant Lines:	216

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💛 - Coveralls

[JohnEfford]

This came about when I was trying to document the Property attribute when running async tasks. I was not able to exercise the code in FSharp which is why I added the Hedgehog.Xunit.CSharp.Tests project. Sorry if it has complicated the merge.

[dharmaturtle]

All good! This draft PR exists because I was sanity checking my ? commit which undos some of your changes - I was trying to figure out why the tests were passing on my machine, and I wanted to see what CICD thought. Eventually I figured out it was due to Task.CompletedTask; switching them to Task.Delay caused the tests to fail, which is what I wanted. I'm guessing the former gets JITed to be synchronous or something; IDK my async knowledge is poor. The failing tests (which is what I wanted) are visible in the most recent commit of the real PR. Closing this because it served its purpose :)