ApplicationAvailabilityBean should log at debug level

[philwebb]

We added more logging in #23098 at INFO but I wonder if DEBUG might be better.

[snicoll]

On a command-line app, upgrading lead to the following:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.5.0)

2021-05-25 14:54:03.391  INFO 33405 --- [           main] o.s.release.checklist.Application        : Starting Application using Java 11.0.7 on snicoll-a01.vmware.com with PID 33405 (/Users/snicoll/tools/releases/boot-release/spring-release-checklist.jar started by snicoll in /Users/snicoll/tools/releases/boot-release)
2021-05-25 14:54:03.393  INFO 33405 --- [           main] o.s.release.checklist.Application        : The following profiles are active: release-env,2.4.x
2021-05-25 14:54:03.970  INFO 33405 --- [           main] o.s.release.checklist.Application        : Started Application in 0.96 seconds (JVM running for 1.342)
2021-05-25 14:54:03.971  INFO 33405 --- [           main] o.s.b.a.ApplicationAvailabilityBean      : Application availability state LivenessState changed to CORRECT
2021-05-25 14:54:04.069  INFO 33405 --- [           main] o.s.r.c.ReleaseCheckListGenerator        :
========================================
Generated checklist at /Users/snicoll/tools/releases/boot-release/spring-boot-2.4.5.adoc
========================================
2021-05-25 14:54:04.070  INFO 33405 --- [           main] o.s.b.a.ApplicationAvailabilityBean      : Application availability state ReadinessState changed to ACCEPTING_TRAFFIC

+1 for moving these to debug.