Clean up no_search mode to not use search_strategy (#643)

## Describe your changes
We currently use a hacky method to run `no_search` using
`search_strategy`. This makes the logic confusing and unnecessarily
complicated.

Clean up the logic by just iterating over the pass flows directly. 

## Checklist before requesting a review
- [ ] Add unit tests for this change.
- [ ] Make sure all tests can pass.
- [ ] Update documents if necessary.
- [ ] Format your code by running `pre-commit run --all-files`
- [ ] Is this a user-facing change? If yes, give a description of this
change to be included in the release notes.

## (Optional) Issue link

olive/engine/engine.py

@@ -467,66 +467,30 @@ def run_no_search(
         output_dir: str = None,
         output_name: str = None,
     ):
-        """Run all the registered Olive passes in no-search model where search strategy is None."""
-        assert (
-            self.search_strategy._config.execution_order == "joint"
-        ), "run_no_search only supports default joint execution order"
-
+        """Run all the registered Olive pass flows in no-search mode."""
         for pass_item in self.passes.values():
             if len(pass_item["pass"].search_space()) > 0:
                 pass_name = pass_item["name"]
                 raise ValueError(f"Pass {pass_name} has search space but search strategy is None")
 
-        evaluator_config = self.evaluator_for_pass(list(self.passes.keys())[-1])
-        if evaluator_config is None:
-            # provide dummy objective
-            objective_dict = {"dummy": {"higher_is_better": True, "goal": 0}}
-        else:
-            objective_dict = self.resolve_objectives(
-                input_model_config, input_model_id, data_root, evaluator_config.metrics, accelerator_spec
-            )
-
-        # initialize the search strategy
-        self.search_strategy.initialize(self.pass_flows_search_spaces, input_model_id, objective_dict)
-
-        iter_num = 0
         output_models = {}
-        while True:
-            iter_num += 1
-
-            # get the next step
-            next_step = self.search_strategy.next_step()
-
-            if iter_num == 1:
-                assert next_step is not None, "Search strategy returned None for the first step"
-            # if no more steps, break
-            if next_step is None:
-                break
-
-            assert iter_num <= len(self.pass_flows), "No more pass flows to run"
-
-            # get the model id of the first input model
-            model_id = next_step["model_id"]
-            if model_id == input_model_id:
-                model_config = input_model_config
-            else:
-                model_config = self._load_model(model_id)
-
-            logger.debug(f"Step no search with search point {next_step['search_point']} ...")
+        for pass_flow in self.pass_flows:
+            # search point is empty since there is no search
+            passes_to_run = [(pass_id, {}) for pass_id in pass_flow]
 
-            # run all the passes in the step
+            # run all the passes in the pass flow
+            logger.debug(f"Running {pass_flow} with no search ...")
             should_prune, signal, model_ids = self._run_passes(
-                next_step["passes"], model_config, model_id, data_root, accelerator_spec
+                passes_to_run, input_model_config, input_model_id, data_root, accelerator_spec
             )
 
-            pass_flow = self.pass_flows[iter_num - 1]
             if should_prune:
                 failed_pass = pass_flow[len(model_ids)]
                 logger.warning(f"Flow {pass_flow} is pruned due to failed or invalid config for pass '{failed_pass}'")
                 continue
 
             # names of the output models of the passes
-            pass_output_names = [self.passes[pass_name]["output_name"] for pass_name, _ in next_step["passes"]]
+            pass_output_names = [self.passes[pass_id]["output_name"] for pass_id in pass_flow]
             pass_output_names = [f"{name}_{accelerator_spec}" if name else None for name in pass_output_names]
 
             # output dir with pass flow