Additional experiments appearing in the global warming level diagnostic

[lewisjared]

The problem

https://github.com/Climate-REF/climate-ref/blob/main/packages/climate-ref-esmvaltool/tests/unit/test_solve_regression/test_solve_regression_climate_at_global_warming_levels_.yml

Definition of "done"

solve regression test only has historical and target experiment

Additional context

[lewisjared]

We should also add the scen7-xx experiments to the CMIP7 data requirement: https://cmip-data-request.github.io/cmip7-dreq-webview/latest/experiments.html