Fix OpenJDK JRE versions

Previously, Groovy applications that use @Grab were affected by
problems in the _25 version of the JRE.  This change fixes the version
of the JRE to _21 until those bugs are fixed.

[#55382524]
Merge 55382524-fix-openjdk-version to master

[Completes #55382524]
Use Spring CLI TAR file

This change causes the Spring Boot CLI container to use a TAR file
rather than a ZIP file.  This simplifies the extraction process.

[#55377304]
Merge 55377304-spring-boot-tar to master

[Completes #55377304]
Merge branch 'master' of github.com:cloudfoundry/java-buildpack