Test updates

[Kritner]

Description

• Adds additional tests around exceptions within test runs
• Additional checks of Task vs void use within tests.

Type of Change

Use an x in between the [ ] for each line applicable to the type of change for this PR

• Bug fix
• New Feature
• Documentation
• Code improvement
• Breaking change - if a public API changes, or any change that DOES or MAY require a major revision to the NuGet package version due to semver.
• Unit tests
• Code samples
• Added your repository URL to the readme because you make use of this super cool package! ;)
• Other

Describe testing that was performed for your change

Added only test code

Checklist

• Read the https://github.com/Kritner-Blogs/FlakyTest.XUnit/blob/main/CONTRIBUTING.md
• Ran unit tests and ensured they passed
• Added unit tests where applicable
• Referenced an issue where applicable
• Ran dotnet-format locally