refactor: async error handling and future tracking improvements

- Update async procedures to use explicit raises annotation
- Modify TrackedFutures to handle futures with no raised exceptions
- Replace `asyncSpawn` with explicit future tracking
- Update test suites to use `unittest2`
- Standardize error handling across network and async components
- Remove deprecated error handling patterns

This commit introduces a more robust approach to async error handling and future management, improving type safety and reducing potential runtime errors.

codex/node.nim

@@ -286,7 +286,7 @@ proc streamEntireDataset(
       except CatchableError as exc:
         trace "Error erasure decoding manifest", manifestCid, exc = exc.msg
 
-    jobs.add(erasureJob())
+    self.trackedFutures.track(erasureJob())
 
   jobs.add(self.fetchDatasetAsync(manifest))
 

tests/codex/sales/states/testfilling.nim

@@ -1,3 +1,4 @@
+import pkg/unittest2
 import pkg/questionable
 import pkg/codex/contracts/requests
 import pkg/codex/sales/states/filling