introduce hudson.Util#fixNull(value, defaultValue)

[JENKINS-46725] - Update jnr-posix to 3.0.45 to prevent Illegal Reflective access warnings

[JENKINS-51903] - Allow specifying multiple Java versions in Jenkinsfile

Backports Jenkinsfile from the java11-support branch

Upgrade to latest version of Remoting.

Primarily this eliminates a potential deadlock in managing the ProtocolStack.

Remove SECURITY-218 class import from TcpSlaveAgentListener test.

Signed-off-by: NNicolas De Loof <nicolas.deloof@gmail.com>

YAGNI.

[JENKINS-53593] Fix class loader error specific to OS.

* JENKINS-53353 Do not cache results of View.getActions()

Plugins that may affect the view, eg via TransientViewActionFactory
that get installed _after_ a `view` has been initally viewed
will not be able to add anything to the view if the results
of getActions() are cached.

* JENKINS-53353 Removed unnecessary synchronization

* JENKINS-53353 Whitespace

* JENKINS-53353 Restored (and deprecated) updateTransientActions

to maintain backwards compatibility.

[JENKINS-46523] - Make UnixReflection class compatible with Java 11, remove pre-Java 8 reflection (#3650)

* [JENKINS-46523] - Make UnixReflection class compatble with Java 9+, remover pre-Java-8 code

Ideally this logic should be replaced by Multi-Release JAR

* [JENKINS-46523] - FindBugs annotations complicate the code here

* [JENKINS-53799 ] - Explicitly reference the JIRA ticket in the error message

[JENKINS-53721] - Add getter/setter to EnvVars so the envinject plugin can set Platform safely (#3639)

[JENKINS-53721] - Add getter/setter to EnvVars so the envinject plugin can set Platform safely

[JENKINS-53693] - Ignore java.xml components in Mocked core tests

JDK-11 support: refactor code to avoid underscore variable names

[JENKINS-53793] - Suppress DMI_COLLECTION_OF_URLS in ClassicPluginStrategy

It is require to make the tests passing on Java 11, but apparently it also speeds up tests on Java 8.

Exclude UI screw

It starts failing FindBugs runs against Java 11.
The implementation is not efficient, but it should not be a serious issue in this case

Javadoc: Cleanup obsolete <tt> tags from package.html

[JENKINS-52019] - Update Groovy from 2.4.11 to 2.4.12 to pick up fixes towards Java 11 support

* Added Spanish translation for 'Build triggers' section in the UI

* Copyright changes to MIT license

[JENKINS-53401] Tie nodeProperties to the current node for save purpose

Javadoc: cleanup `tt` tags from Javadoc (prohibited in JDK11)

* [JENKINS-53693] - Update PowerMock and Mockito to a Java11-compatible version

* [JENKINS-53693] - Fix tests which depend on mocking

* [JENKINS-53693] - Apply fixes to PowerMock

[JENKINS-52024] - Update sezpoz to 1.13