Refactor Alphabetical implementation and tests (#7370)

* Improve Alphabetical implementation, tests and documentation

* Workaround SpotBugs false positive in parameterized tests

Replaced boolean literals with Boolean.TRUE/FALSE in Arguments.of(...)
to avoid SpotBugs warning (NAB_NEEDLESS_BOOLEAN_CONSTANT_CONVERSION).

This is a false positive caused by JUnit's Object... varargs
requiring auto-boxing.