refactor: Moved ITestFixtureFactory from Experiment.Xunit to

Experiment.
docs: Addressed release notes(v2) for moving some interfaces.
dev: Introduced TestFixtureFactory.
test: Fixed false-positive.
dev: Implemented TestFixtureFactory.
docs: Documented TestFixtureFactory.
docs: Addressed release notes to be more informative.
Merge pull request #46 from jwChung/test-fixture-factory

Introduce the new test fixture factory [skip ci]