Move Spring AMQP 0.9 support to spring-boot-rabbitmq

Now that Spring AMQP supports AMQP 1.0 as well, we need to straighten
out our existing support. AMQP 0.9 is RabbitMQ specific, so we can no
longer refer it to "amqp". This commit migrates the existing support
to spring-boot-rabbitmq and renames the starters as well.

For continuity, users should migrate from "spring-boot-starter-amqp"
to "spring-boot-starter-rabbitmq". While the root package has been
changed for consistency, most names are the same, including
configuration properties still in the "spring.rabbitmq" namespace.

Keys to configure the version of the RabbitMQ clients have migrated to
'rabbitmq.client' and 'rabbitmq.stream.client' respectively.

Closes gh-49677

starter/spring-boot-starter-rabbitmq-test/build.gradle

@@ -18,10 +18,10 @@ plugins {
 	id "org.springframework.boot.starter"
 }
 
-description = "Starter for testing Spring AMQP and Rabbit MQ"
+description = "Starter for testing RabbitMQ messaging and streaming broker"
 
 dependencies {
-	api(project(":starter:spring-boot-starter-amqp"))
+	api(project(":starter:spring-boot-starter-rabbitmq"))
 	api(project(":starter:spring-boot-starter-test"))
 
 	api("org.springframework.amqp:spring-rabbit-test")

starter/spring-boot-starter-rabbitmq/build.gradle

@@ -18,10 +18,10 @@ plugins {
 	id "org.springframework.boot.starter"
 }
 
-description = "Starter for using Spring AMQP and Rabbit MQ"
+description = "Starter for using RabbitMQ messaging and streaming broker"
 
 dependencies {
 	api(project(":starter:spring-boot-starter"))
 
-	api(project(":module:spring-boot-amqp"))
+	api(project(":module:spring-boot-rabbitmq"))
 }