Bringing this to the parity with ParameterizedJobMixIn.doBuild()

Instead of returning JSON, it returns "201 Created" and responds with the location of the queue item, through which the caller can track how it passes through the queue and eventually gets built/cancelled.

The approach in pull request #750 that relies on
AbstractProject.getQueueItem() is inherently unreliable, because
item can be immediately built before the JSON is rendered, or it might
corresponds to other queued items if the build supports concurrent
builds, etc.

[JENKINS-20974] RunParameter with filtering enabled should not include builds which have not completed

[FIXED JENKINS-21622] Release workspace leases (and avoid @2) even if post-build actions throw LinkageError.

(Forgot that Run’s are unmarshalled in place after a special constructor is called, so there is no need for readResolve or other tricks.)
Also calling RunListener.onDeleted outside of the Run lock to avoid problems with things like ChangeLogHistoryRunListener.

Hoping nobody uses it programmatically.

Also, added @Restricted to the new one.

Reduce classloader activities.

This brings in Stapler and commons bean-utils that we don't need on the
slaves.

And moving the permissions checks in BuildTrigger from being hardcoded in execute to being overridable in Dependency.
This has two benefits:
· We can restore the previous form validation logic predicting whether Item.BUILD will be available.
· A (true) Trigger could check Item.READ on the upstream project
  under the authentication that the downstream project would have if it were to be built.
  (This part is not yet implemented; probably will want to make this replace the current pseudotriggers.)

[JENKINS-16956] Make BuildTrigger.execute pay attention to build permissions, rather than checking the configuring user.

When a QueueItemAuthenticator is in use, report the user under whose authentication the build is running.

[FIXED JENKINS-22382] Need to restore deprecated overload of BuildAuthorizationToken.checkPermission for binary compatibility.

UI elements should explicitly ask for .fullDisplayName.

[JENKINS-22326] Calling into foreign code from a toString method, like Queue.Item.getWhy → QueueTaskDispatcher, is unsafe.

java.lang.NullPointerException
	at hudson.model.Job.getBuildDir(Job.java:790)
	at hudson.model.Run.getRootDir(Run.java:993)
	at hudson.model.Run.getLogFile(Run.java:1306)
	at hudson.model.Run.execute(Run.java:1664)
	at hudson.maven.MavenBuild.access$900(MavenBuild.java:94)
	at hudson.maven.MavenBuild$ProxyImpl2.close(MavenBuild.java:636)
	at hudson.maven.AbstractMavenBuilder.end(AbstractMavenBuilder.java:106)
	at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.doRun(MavenModuleSetBuild.java:839)
	at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:523)
	at hudson.model.Run.execute(Run.java:1688)
	at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:519)
	at hudson.model.ResourceController.execute(ResourceController.java:88)
	at hudson.model.Executor.run(Executor.java:231)
java.lang.NullPointerException
	at hudson.model.BuildStepListener.all(BuildStepListener.java:31)
	at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:739)
	at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:714)
	at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.cleanUp(MavenModuleSetBuild.java:1054)
	at hudson.model.Run.execute(Run.java:1733)
	at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:519)
	at hudson.model.ResourceController.execute(ResourceController.java:88)
	at hudson.model.Executor.run(Executor.java:231)