Restore the 'javax.xml.bind:jaxb-api' exclusion from `xmlunit-core`
which is actually required when using Maven on Java 9+.
The `CheckClasspathForUnnecessaryExclusions` cannot deal with profile
specific dependencies so an exception has been hard coded.
See gh-28332
Previously, the project version was used while filtering the apps
source during syncing but it was not considered as an input to
the task. This could result in the syncing being skipped even though
the project's version had changed.
This commit introduces a new custom task to make the configuration
more declarative and to allow the necessary input configuration to be
done in a single place.
Closes gh-28197
Previously, the optional configuration was added to the compile and
runtime classpaths of each source set and the the javadoc classpath
as well. This had a few disadvantages, the most notable of which is
that it meant that the configuration was ifrst resolved and then
the outcome of the resolution was added to the compile and runtime
classpaths. As a result, none of the attributes on the compile and
runtime classpaths were considered to influence variant selection.
This commit reworks the optional dependencies plugin so that the
compile and runtime classpaths of each source set are now configured
to extend from the optional configuration. This allows each
classpath configuration's attributes to influence the dependencies
that are selected from the optional configuration during resolution.
For example, when resolving the compile classpath, compile
dependencies (Usage.JAVA_API) will be selected and when resolving the
runtime classpath, runtime dependencies (Usage.JAVA_RUNTIME) will be
selected.
The above-described change means that runtime dependencies of an
optional dependencies will no longer leak into the compile classpath.
As a result of this, our Gradle plugin's test infrastructure has
been updated so that it no longer references runtime dependencies of
the Kotlin Gradle plugin at compile time.
Closes gh-27965
