AMQP-428: Add Logback `AmqpAppender`

JIRA: https://jira.spring.io/browse/AMQP-433, https://jira.spring.io/browse/AMQP-428

Fix `amqp.rabbit.log4j.AmqpAppender` JavaDoc typo

Polishing

Add category abbreviation [o.s.a.r.l.AmqpAppenderIntegrationTests].

Retain full category in AMQP headers.
AMQP-432: Properly convert BasicProperties values to and from
MessageProperties

JIRA: https://jira.spring.io/browse/AMQP-432

Previously `DefaultMessagePropertiesConverter` converted just
`LongString`,
but BasicProperties may contain List and Map values with nested
LongStrings. Values unsupported by AMQP which are contained in Lists or
Maps are also not converted from `MessageProperties` to
`BasicProperties`.

Add logic to properly convert from LongString values nested in
Lists/Maps.
Add logic to properly convert unsupported values nested in Lists/Maps to
Strings.

**Cherry-pick to 1.3.x**

Code style polishing
AMQP-430 Fix Package Tangle

JIRA: https://jira.spring.io/browse/AMQP-430

Annotation support introduced a tangle between config and annotation.

Polishing - Move Test Cases
AMQP-431: Add `RabbitTemplate.recoveryCallback`

JIRA: https://jira.spring.io/browse/AMQP-431
AMQP-431: Address PR comments