Simplify LTI integration test to speed up tests

[pavelacamposp]

Description

This PR simplifies the LTI controller integration test to reduce the runtime of the CI pipeline by integrating the following changes:

• Simplify the dynamics of the test LTI model in test_lti_model.yaml.
• Update the LTI controller parameters for the new test model in test_lti_dd_mpc_params.yaml. The new parameters result in a controller that requires less computation effort.
• Reduce the number of simulation steps in the LTI controller integration test test_lti_dd_mpc_integration.py, as the new test system is simpler to control.

Type of change

• Chore (non-code task, such as docs or dependency update)

Checklist

• I have run the pre-commit checks either with pre-commit run --all or by integrating pre-commit into my workflow
• I have added tests to ensure my changes work as expected without errors (if applicable)
• I have run the test suite locally with pytest and verified that all tests pass
• I have provided clear context, rationale, and linked any related issues (if applicable)
• I have updated the documentation (if applicable)

[pavelacamposp]

The simplified LTI controller integration test reduces its runtime by approximately 1 minute (from 3m 30s to 2m 20s, based on previous test runs). Merging now.