reduceToCompileOnlyApiDependency does not work for Guava

[jjohannes]

The runtime variants are not named runtimeElements in their metadata as there are two runtime variants.

[britter]

We looked at the code together during the team meeting and realized that the ComponentMetadataContext give access to the AttributesContainer. So instead of looking at names, we can check for the presence of the JAVA_RUNTIME attribute on the variant.

In addition we should check that the Category attribute is library.

[jjohannes]

This is implemented in 2.4, but we needed to use Gradle internals.
Follow up: gradle/gradle#33769