Warn on SDK/CLI creation of libfuzzer_coverage task (#1944)

The old `libfuzzer_coverage` task dumps binary sancov tables. Its output is not usable on its own. This task has been superseded by the generic `coverage` task (which produces actual modoffset and source line coverage).

Add a CLI warning if it is used, in preparation for removing it.

src/cli/onefuzz/api.py

@@ -26,6 +26,7 @@
     responses,
     webhooks,
 )
+from onefuzztypes.enums import TaskType
 from pydantic import BaseModel
 from six.moves import input  # workaround for static analysis
 
@@ -802,7 +803,7 @@ def create_with_config(self, config: models.TaskConfig) -> models.Task:
     def create(
         self,
         job_id: UUID_EXPANSION,
-        task_type: enums.TaskType,
+        task_type: TaskType,
         target_exe: str,
         containers: List[Tuple[enums.ContainerType, primitives.Container]],
         *,
@@ -852,6 +853,13 @@ def create(
 
         self.logger.debug("creating task: %s", task_type)
 
+        if task_type == TaskType.libfuzzer_coverage:
+            self.logger.warning(
+                "DEPRECATED: the `libfuzzer_coverage` task type is deprecated. "
+                "It will be removed in an upcoming release. "
+                "Please migrate to the `coverage` task type."
+            )
+
         job_id_expanded = self._disambiguate_uuid(
             "job_id",
             job_id,