Ensure queued deltas are published before shutdown

[MetRonnie]

Closes #5092

Fix bug where the final deltas were not being published before stopping the WorkflowRuntimeServer at shutdown

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• No dependency changes
• Tests are included
• CHANGES.md entry included if this is a change that can affect users
• No docs needed
• If this is a bug fix, PRs raised to both master and the relevant maintenance branch.

[oliver-sanders]

aeaeee9 Looks good to me. The tidying and shutdown fiddling (unrelated to the bugfix) should go onto the 8.1.0 milestone (can cherrypick onto the merge PR or whatever).

[MetRonnie]

I've removed most of that from this branch, but kept the improved error logging and fixes to a few type annotations that were incorrect

[dwsutherland]

LGTM 👍