Add Sequential high-d GS tests with new test harness (facebook#2940)

Summary:

Lena recently added a test harness which will allow us to quickly test a variety of GS configurations at the GS level, previously we were testing them at the client level, but this is a bit higher than we may always access the stack so it's good to have both sets of tests.

This diff adds tests for high-d seq gs:
- tests that high-d seq works as expected and gens
- also tests that experiment_properties if n and arms per node is none


Follow up diffs will test:
- quickbo gs
- ebashr fixes that came to light during bug bash
- multi-task models

Reviewed By: lena-kashtelyan

Differential Revision: D64807079

ax/utils/testing/core_stubs.py

@@ -841,7 +841,9 @@ def get_experiment_with_observations(
     return exp
 
 
-def get_high_dimensional_branin_experiment(with_batch: bool = False) -> Experiment:
+def get_high_dimensional_branin_experiment(
+    with_batch: bool = False, with_status_quo: bool = False
+) -> Experiment:
     search_space = SearchSpace(
         # pyre-fixme[6]: In call `SearchSpace.__init__`, for 1st parameter `parameters`
         # expected `List[Parameter]` but got `List[RangeParameter]`.
@@ -865,6 +867,7 @@ def get_high_dimensional_branin_experiment(with_batch: bool = False) -> Experime
         ],
     )
 
+    sq_parameters = {f"x{i}": 1.0 if i < 25 else 2.0 for i in range(50)}
     optimization_config = OptimizationConfig(
         objective=Objective(
             metric=BraninMetric(
@@ -880,6 +883,8 @@ def get_high_dimensional_branin_experiment(with_batch: bool = False) -> Experime
         search_space=search_space,
         optimization_config=optimization_config,
         runner=SyntheticRunner(),
+        # pyre-fixme[6]: expects a union type for val instead of defined {str: float}
+        status_quo=Arm(sq_parameters) if with_status_quo else None,
     )
     if with_batch:
         sobol_generator = get_sobol(search_space=exp.search_space)