🐛 Use allowed-failures and skips equally

Before this patch, `allowed-failures` did not contribute to the
overall computed outcome due to a bug in the checking logic. This
change refactors the data strucutures used to simplify the check and
reduce its complexity in general.

Fixes #23

src/normalize_needed_jobs_status.py

@@ -153,13 +153,17 @@ def main(argv):
             )
         return 1
 
+    allowed_outcome_map = {}
+    for job_name in jobs.keys():
+        allowed_outcome_map[job_name] = {'success'}
+        if job_name in jobs_allowed_to_be_skipped:
+            allowed_outcome_map[job_name].add('skipped')
+        if job_name in jobs_allowed_to_fail:
+            allowed_outcome_map[job_name].add('failure')
 
     job_matrix_succeeded = all(
-        job['result'] == 'success' for name, job in jobs.items()
-        if name not in (jobs_allowed_to_fail | jobs_allowed_to_be_skipped)
-    ) and all(
-        job['result'] in {'skipped', 'success'} for name, job in jobs.items()
-        if name in jobs_allowed_to_be_skipped
+        job['result'] in allowed_outcome_map[name]
+        for name, job in jobs.items()
     )
     set_final_result_outputs(job_matrix_succeeded)