Add –skip-unit-tests parameter to tuist test command

Why is this needed?

Currently, the tuist test command runs all tests in a project, including unit tests and UI tests. In some workflows, developers may want to run only UI tests or other specific test subsets, skipping unit tests to save time or focus test runs.

Steps to address the need

Introduce a new –skip-unit-tests boolean flag to the tuist test command. When this parameter is used, the test runner will exclude all unit test targets from execution, running only other test types (such as UI tests).