test(twap): table-driven test for AfterEpochEnd

[p0mvn]

Background

#2294 added pruning logic to the AfterEpochEnd hook.

We should add some test cases to ensure full coverage of the hook

Suggested Design

• test that it is no-op if current epoch != prune epoch
• test that pruning occurs with the correct "time to keep records" set
  • Ensure that records earlier than the expected time are deleted
  • Ensure that records later or at the expected time are kept
• test that it does not panic on pruning error

Acceptance Criteria

• full test coverage as per suggested design

[p0mvn]

This is blocked by #2294

[p0mvn]

Closed by #2443