(VDB-354) Queue unrecognized storage diffs

- If we recognize a storage diff as coming from a watched contract but
  don't recognize the key, queue it for retrying later (after we've seen
  an event that might help us recognize the key)
- Remove unused errs and args
- Panic on unrecognized types (should not happen)

pkg/transformers/test_data/mocks/storage_queue.go

@@ -0,0 +1,15 @@
+package mocks
+
+import (
+	"github.com/vulcanize/vulcanizedb/pkg/transformers/storage_diffs/shared"
+)
+
+type MockStorageQueue struct {
+	AddCalled bool
+	AddError  error
+}
+
+func (queue *MockStorageQueue) Add(row shared.StorageDiffRow) error {
+	queue.AddCalled = true
+	return queue.AddError
+}