Make workflow-basic-steps compatible with Guava 21.0 and newer

[basil]

Discovered in jenkinsci/bom#423. Like jenkinsci/workflow-support-plugin#114 and jenkinsci/git-client-plugin#686, but for workflow-basic-steps.

workflow-basic-steps previously used MoreExecutors#sameThreadExecutor from Guava, which was removed in version 21.0 in favor of MoreExecutors#newDirectExecutorService. This PR uses reflection to first try to call MoreExecutors#newDirectExecutorService but then call MoreExecutors#sameThreadExecutor if the first method is not available to support both older and newer versions of Guava.

[timja]

@jenkinsci/workflow-basic-steps-plugin-developers please

[timja]

@basil you may want to pull in #149 as well, incremental doesn't work otherwise in bom for PCT

I've created #150 anyway

[jglick]

Probably OK though

workflow-basic-steps-plugin/src/main/java/org/jenkinsci/plugins/workflow/steps/TimeoutStepExecution.java

Line 173 in 0016470

// TODO would use Futures.addCallback but this is still @Beta in Guava 19 and the Pipeline copy is in workflow-support on which we have no dep

[timja]

@car-roll

[timja]

@car-roll is it possible to get a release please?

Ideally including #144

[car-roll]

@timja no problem, once i've finished going through #144, and the other approvals clear, I'll do a release