Add NUnit Analyzers

[rubo]

Changes

• Added NUnit Analyzers as recommended by the NUnit team. Assertions have been updated by analyzers automatically, and a few of them have been revised manually. For instance:

  -Assert.AreEqual(expected, actual);
  +Assert.That(actual, Is.EqualTo(expected));

• All test projects referencing NUnit package now reference NUnit.Analyzers package as well

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Remarks

The analyzers have already caught a few issues and fixed them.

[LukaszRozmej]

I still prefer FluentAssertions :)