During working on HHH-14227, I found there are many minor issues in ActionQueue, including:
failure to set LinkedHashMap's constructor parameter correctly;
unused temporary variable;
unnecessary down casting;
unnecessary nullness checking;
possible simplification to BatchIdentifier
Given that we have improved the insert ordering testing cases, it is good timing to consider improve ActionQueue, which is important and is definitively a hot spot.
Note that the scope of this ticket only includes minor issue fixing, excluding fundamental sorting refactoring, etc.
Only a subset of the proposed changes were applied; see the PR for details.