Slightly improve the test framework

[LuernOutOfOrder]

This pull request introduces a new TestSuiteBehavior enum to allow marking test suites as "Default" or "Skipped", and updates the test framework to support skipping both test suites and individual test cases. It also improves test result reporting to account for skipped tests and suites. Additionally, it refactors the test suite initialization and registration process, moving the suite registration into a dedicated suites module for better organization. Some minor code style and import ordering changes are also included.

Test framework enhancements:

• Added the TestSuiteBehavior enum and updated the TestSuite struct and initialization to support marking test suites as "Default" or "Skipped". Test cases also gain a Skipped behavior. [1] [2]
• Updated the test runner logic to skip suites and test cases marked as skipped, and to track/report the number of skipped tests and suites in the summary output. [1] [2] [3]

Test suite and case usage:

• Updated all test suite definitions throughout the codebase to set the new behavior field, typically to TestSuiteBehavior::Default (or Skipped for the NS16550 suite as an example). [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Test suite registration refactor:

• Moved the suite registration logic into a new suites module, simplifying the main mod.rs and making suite management more maintainable. [1] [2]

Code cleanup and style:

• Reordered imports for consistency and clarity across several files. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Documentation:

• Updated documentation to reflect the new test suite and test case behaviors, and clarified file paths in examples. [1] [2]

Other minor changes include updating the crate version in Cargo.toml to 0.3.2.