Cortex-M backend: Refactor ConvertToCortexMPass (pytorch#20070)

Change to use the general AtenToDialectPass structure,
quantized_op_fusion_pass
to be changed similarly in an upcoming PR.

Removes the 1-1 ensure check as it was to restrictive, cortex-m backend
needs to both insert scratch nodes and for BMM an additional transpose
at the time of dialect replacement.

Bonus small fix: Moves yolo import into test to avoid download at test
collection time

---------

Signed-off-by: Adrian Lundell <adrian.lundell@arm.com>

Author: AdrianLundell

backends/cortex_m/passes/BUCK

@@ -29,8 +29,8 @@ fbcode_target(_kind = runtime.python_library,
     name="cortex_passes",
     srcs=[
         "activation_fusion_pass.py",
+        "aten_to_cortex_m_pass.py",
         "clamp_hardswish_pass.py",
-        "convert_to_cortex_m_pass.py",
         "cortex_m_pass.py",
         "cortex_m_pass_manager.py",
         "decompose_hardswish_pass.py",
@@ -45,8 +45,10 @@ fbcode_target(_kind = runtime.python_library,
         "//executorch/backends/cortex_m/ops:ops",
         "//executorch/backends/cortex_m/passes:passes_utils",
         "//executorch/backends/cortex_m/passes:replace_quant_nodes_pass",
+        "//executorch/backends/transforms:aten_to_dialect_pass",
         "//executorch/backends/transforms:remove_getitem_op",
         "//executorch/backends/transforms:replace_scalar_with_tensor",
+        "//executorch/backends/transforms:utils",
         "//executorch/exir:lib",
         "//executorch/exir:pass_base",
         "//executorch/exir:pass_manager",

backends/cortex_m/passes/__init__.py

@@ -35,8 +35,8 @@ def _ensure_cortex_m_dependencies() -> None:
 
 from .cortex_m_pass import CortexMPass  # noqa  # usort: skip
 from .activation_fusion_pass import ActivationFusionPass  # noqa
+from .aten_to_cortex_m_pass import AtenToCortexMPass  # noqa
 from .clamp_hardswish_pass import ClampHardswishPass  # noqa
-from .convert_to_cortex_m_pass import ConvertToCortexMPass  # noqa
 from .cortex_m_pass import CortexMPass  # noqa
 from .decompose_hardswish_pass import DecomposeHardswishPass  # noqa
 from .decompose_mean_pass import DecomposeMeanPass  # noqa