[JENKINS-22367] Split JDKInstaller to a plugin (#3301)

* [JENKINS-22367] Preparation for split of JDKInstaller to a plugin

* Add split-plugins entry and pending update to war/pom.xml

* Update jdk-tool plugin description

* Fix Findbugs warnings

* Update to HttpComponents Client 4.5

* Preserve formatting in translations of Messages.properties

* Preserve ISO-8859-1 encoding for properties

* Break cycle between jdk-tool and apache-httpcomponents-client-4-api

* Update version numbers after merge

* Add warning for the download from java.sun.com JDK installer

* Fix issues introduced when cleaning up Findbugs errors in 9dbf833

* Use warning class for error message and adjust message text

* Revert "Update to HttpComponents Client 4.5"

This reverts commit 9dbf8334c47eceecea916e105784d4f90415e3c3.

* Findbugs

* Remove JenkinsRule from test that does not use it

* Update version numbers after merge

* Warn when unexpected exceptions are thrown and update new plugin urls

* Update to 2.109-SNAPSHOT

* Address review feedback

* Update to 2.111-SNAPSHOT

* Try to use the agent's default charset to copy the install log

* Update to 2.112-SNAPSHOT

* Remove local module and use snapshot of jdk-tool

* Update to jdk-tool:1.0