Repo maintenance

[olstakh]

This pull request primarily updates documentation for clarity and simplifies the codebase by removing unnecessary using directives and refactoring logic. It also makes a key change to how test collection dependency cycles are handled, improving test execution robustness. The most important changes are:

Documentation improvements:

• Clarified the description of [FactDependsOn] in the README.md, emphasizing its skip logic for upstream dependencies. Also improved the FAQ to explain when and why to use [FactDependsOn] instead of [Fact], and how dependency-aware skipping works. [1] [2]

Codebase simplification and cleanup:

• Removed unused or redundant using directives from multiple files in both the analyzers and test projects, reducing clutter and potential confusion. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]

Test collection dependency handling:

• Changed the behavior in DependencyAwareTestCollectionOrderer so that if a circular dependency is detected, the original test collection order is preserved and tests are allowed to run, instead of throwing an exception and aborting execution. This makes test runs more resilient in the presence of misconfigured dependencies.

Test case comparison logic:

• Refactored TestCaseComparer to use the UniqueID property for equality and hash code computation, simplifying and improving the reliability of test case comparisons.

Dependency skipping logic:

• Refactored DependencySkippingAssemblyRunner to use SkipValidator.ShouldSkipBasedOnCollectionDependencies for deciding when to skip a test collection, and removed the now-redundant internal logic. [1] [2]