[WIP] Unit Test for dashboard

[proy30]

This PR introduces the first unit test for the ImpactX dashboard, leveraging the SeleniumBase library to simulate a simulation run by a user with the GUI.

Key Features

• The unit test runs a simulation using the parameters from the FODO cell example on the GUI. (takes ~1 minute)
• The test is considered successful if the simulation is completed without errors.

Issues

• Dependency on Running Dashboard:
  • The current implementation requires the ImpactX dashboard to run in a separate terminal before executing the test via pytest.
  • Can investigate to potentially have dashboard be launched within the test itself.
  • Unit test is flaky with passing/failing, unsure if this is due to code error or error in pytest implementation. Need to investigate. Started occurring after the implementation of subprocess.
• Adding seleniumbase as a dependency
  • Unsure where to add. (implemented incorrectly)

Checklist

• Implement unit test for impactx-dashboard (testing with FODO cell simulation parameters.
• Automate the dashboard launch within the test.
• Fix flaky unit test
• Include seleniumbase dependency in CI test files
• Include trame dependencies in CI test files
• Fix headless state for ctest

Resolves #667