Include all source artifacts in published sources jars

This commit updates the Gradle build to ensure that the following are
including in published 'sources' jars.

 - Java source code (previously supported)
 - AspectJ source code (previously supported)
 - META-INF/spring.factories
 - META-INF/services/*
 - Java Properties files
 - XML files
 - MIME types files (mime.types)

Issue: SPR-12085
Include Groovy source code in published sources jars

In our Gradle build script, we are now assembling 'sources' jars from
'sourceSets.main.allSource' in order to include Java, Groovy, and
AspectJ source code as well all other appropriate classpath resources.

Issue: SPR-12086