INT-3512: Add `<advice-chain>` to the Aggregator

JIRA: https://jira.spring.io/browse/INT-3512

INT-3512: Fix typos

INT-3512: add `expire-` prefix to the advice sub-elements

INT-3512: Mark `AggregatorWithCustomReleaseStrategyTests` as `LONG_RUNNING_TEST`

Doc Polishing