TransientActionFactory cache simplification

[jglick]

Amending #2582 as proposed in #7932 (comment). New implementation is (IMO) simpler and avoids Guava.

Testing done

Just ran TransientActionFactoryTest.

Proposed changelog entries

• N/A

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[NotMyFault]

/label ready-for-merge

---

This PR is now ready for merge. We will merge it after ~24 hours if there is no negative feedback.
Please see the merge process documentation for more information about the merge process.
Thanks!

[basil]

Causes failures in (at least) hudson.plugins.emailext.plugins.recipients.FailingTestSuspectsRecipientProviderTest, hudson.plugins.jacococoveragecolumn.AbstractJaCoCoCoverageColumnTest, hudson.plugins.jacococoveragecolumn.BranchCoverageColumnTest, hudson.plugins.jacococoveragecolumn.JaCoCoColumnTest, and jenkins.scm.api.SCMRevisionActionTest of the following form:

INFO: Expected 1 instance of jenkins.model.TransientActionFactory$Cache but got 0
[ERROR] Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 1.454 s <<< FAILURE! - in hudson.plugins.emailext.plugins.recipients.FailingTestSuspectsRecipientProviderTest
[ERROR] hudson.plugins.emailext.plugins.recipients.FailingTestSuspectsRecipientProviderTest.testAddRecipients  Time elapsed: 1.446 s  <<< ERROR!
java.lang.IllegalStateException: Expected 1 instance of jenkins.model.TransientActionFactory$Cache but got 0
        at hudson.ExtensionList.lookupSingleton(ExtensionList.java:454)
        at jenkins.model.TransientActionFactory.factoriesFor(TransientActionFactory.java:127)
        at hudson.model.Actionable.getAction(Actionable.java:331)
        at hudson.model.Actionable.getAction(Actionable.java:325)
        at hudson.plugins.emailext.plugins.recipients.FailingTestSuspectsRecipientProvider.addRecipients(FailingTestSuspectsRecipientProvider.java:83)
        at hudson.plugins.emailext.plugins.recipients.TestUtilities.checkRecipients(TestUtilities.java:60)
        at hudson.plugins.emailext.plugins.recipients.FailingTestSuspectsRecipientProviderTest.testAddRecipients(FailingTestSuspectsRecipientProviderTest.java:121)

The failures all go away when this change is reverted. The failures all look like more cases of commit 1089a22 (i.e., mocks). The tests could be adapted in the same way, or TransientActionFactory#factoriesFor loosened to support running in mock context along the lines of e.g.

return ExtensionList.lookup(Cache.class).stream()
        .findFirst()
        .map(Cache::cache)
        .map(classValue -> classValue.get(type))
        .map(classValue -> classValue.get(actionType))
        .orElse(List.of());

[jglick]

More transparent to fix the mock tests I think. Will propose some corrections soon if no one beats me to it.

[basil]

As a courtesy I have released Email Extension 2.99.