Upgrade jclouds from 2.5.0 to 2.6.0

[basil]

Reverting #447, since 2.6.0 contains the fix for JCLOUDS-1620.

jclouds 2.6.0 requires Guice 7.0.0, which is above the version delivered by core (6.0.0), but so far I have found no issue ignoring the upper bounds error and continuing to deliver Guice 6.0.0. Guice 6.0.0 supports both javax and jakarta imports, while 7.0.0 drops support for javax, so 6.0.0 makes more sense for Jenkins. Unfortunately this required adding a few temporary workarounds to the POM file.

Testing done

mvn clean verify, including MinioIntegrationTest

I would appreciate if someone could do a manual test run with an AWS account, since I believe CI unfortunately is not enough.

[basil]

Tested manually by creating a Pipeline job that uploaded an artifact to S3. Verified that the artifact was correctly uploaded and showed up in my S3 bucket. Also verified in the Script Console that loading com.google.gson.Gson from the Artifact Manager on S3 plugin class loader loaded the class from the GSON API plugin's GSON JAR, as before #447, with Jenkins.instance.pluginManager.getPlugin('artifact-manager-s3').classLoader.loadClass('com.google.gson.Gson').protectionDomain.codeSource.