INT-3495 Add `FileTailInChAFBean#setErrorChannel`

JIRA: https://jira.spring.io/browse/INT-3495

**Cherry-pick to 4.0.x & 3.0.x**

INT-3495 Add `error-channel` to `<tail-i-c-a>`

JIRA: https://jira.spring.io/browse/INT-3495

* Fix `AbstractEndpoint` JavaDoc
INT-3496: JMX Metrics: Int->Long for all `count`

JIRA: https://jira.spring.io/browse/INT-3496

**Cherry-pick to 4.0.x & 3.0.x**
INT-3496: revert `int` methods and introduce `long` methods for `count` metrics