Fix/dynamic data tests

[chrismclarke]

PR Checklist

• PR title descriptive (can be used in release notes)

Description

• Fix issue where dynamic data service does not properly clear data when prompted to reset. I expect this is down to memory management and only really impacts testing environment, so small hack/workaround included just to check for rows post initial creation and delete accordingly.
• Fix tests to include missing await for before hook flow reset
• Add test for flow reset method
• Code tidying for tests
• Code tidying for some of the service collection creation methods

NOTE
Builds on #2157 so should merge after to see clean diffs
Code updates in 9990c5a

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