handle libfuzzer fuzzing non-zero exits better (#381)

When running libfuzzer in 'fuzzing' mode, we expect the following on exit.

If the exit code is zero, crashing input isn't required.  This happens if the user specifies '-runs=N'

If the exit code is non-zero, then crashes are expected.  In practice, there are two causes to non-zero exits.
1. If the binary can't execute for some reason, like a missing prerequisite
2. If the binary _can_ execute, sometimes the sanitizers are put in such a bad place that they are unable to record the input that caused the crash.

This PR enables handling these two non-zero exit cases.

1. Optionally verify the libfuzzer target loads appropriately using `target_exe -help=1`.  This allows failing faster in the common issues, such a missing prerequisite library.
2. Optionally allow non-zero exits without crashes to be a warning, rather than a task failure.

src/cli/onefuzz/api.py

@@ -777,6 +777,8 @@ class Tasks(Endpoint):
         check_asan_log: bool = False,
         check_debugger: bool = True,
         check_retry_count: Optional[int] = None,
+        check_fuzzer_help: Optional[bool] = None,
+        expect_crash_on_failure: Optional[bool] = None,
         debug: Optional[List[enums.TaskDebugFlag]] = None,
         duration: int = 24,
         ensemble_sync_delay: Optional[int] = None,
@@ -851,6 +853,8 @@ class Tasks(Endpoint):
                 check_asan_log=check_asan_log,
                 check_debugger=check_debugger,
                 check_retry_count=check_retry_count,
+                check_fuzzer_help=check_fuzzer_help,
+                expect_crash_on_failure=expect_crash_on_failure,
                 duration=duration,
                 ensemble_sync_delay=ensemble_sync_delay,
                 generator_exe=generator_exe,