Fix hexagon test.

 * previously I believe we required interface_api == "c", but
   this really means to generate C API bindings, and we are generating
   "packed" bindings.
 * I think "c" was chosen here because the distinction between
   interface-api and use-unpacked-api is confusing. "c" interface-api
   means to generate an entrypoint API for microcontrollers that
   accepts bare data buffers. "packed" interface-api means to generate
   a TVMBackendPackedCFunc entrypoint. use-unpacked-api forms the same
   determination for the operator functions.
 * A further confusion here is that there are two ways to call
   "packed" operator functions: tir.tvm_builtin_call_packed and
   tir.tvm_builtin_call_cpacked. This distinction describes whether or
   not to late-bind calls via TVMBackendGetFuncFromEnv. Right now, AOT
   only ever requires call_cpacked because target_host == target, and
   for all suitable target_host, we expect a single DSO-exportable
   runtime.Module. When we move away from this by introducing
   heterogeneous target support to AOT, we can use this as a condition
   to help us choose between call_cpacked and call_packed (and
   possibly add a compile-time option to assert it is call_cpacked,
   for situations where we really don't want call_packed).

tests/python/contrib/test_hexagon/test_launcher.py

@@ -530,7 +530,7 @@ def test_aot_executor_multiple_conv2d(
             params=params,
             target=tvm.target.Target(target_hexagon, host="c"),
             runtime=Runtime("cpp"),
-            executor=Executor("aot", {"unpacked-api": False, "interface-api": "c"}),
+            executor=Executor("aot", {"unpacked-api": False, "interface-api": "packed"}),
         )
         # Uncomment this once the workaround is not needed.
         # lowered.export_library(