[JENKINS 60920] header breadcrumbs CSS update (#4463)

* New styles for breadcrumbs and warnings monitor

* Adds the svgxuse polyfill for svg sprites on IE 11

* Created new styles for the page header

- Used the material icons svg sprites to deliver the icons
- Icons are rendered using a <svg> tag

* Create new base styles file and undo changes to the layout-common and style css files

* Fixes and refactor for the new UI CSS code

* Make the new header color and logo section opt-in

- The new UI can be toggled with the -Dui.enableNewUi=true flag

* Rename and refactor the page-header css

- Rename the css class namespace from .main-header to .page-header
- Page header CSS moved into a modules folder and now included on the new-base-styles.css. This is done to avoid loading a separate file everytime.
- Extracted color variables to their own file

* Updated localization for header and admin monitor

- The pageHeader template receives localization strings as props
- Missing translation for the admin monitor on the it, bg and pl locales

* Update core/src/main/resources/lib/layout/layout.jelly

Co-Authored-By: Tim Jacomb <t.jacomb@kainos.com>

* Most measurements migrated to REMs

* Code cleanup and apply new-ui toggle to the html.jelly file

* Breadcrumb fixes

- Reverts breadcrumb link styling to use nested selectors instead of the .breadcrumbs__link class. The reason is that several plugins would break.
- Shifted margins so that breadcrumbs can be fullwidth in the absence of the auto refresh link

* Implemented some fixes from the feedback received

- Removed box shadow webkit prefix
- Fixed formatting on the breadcrumbs.css and layout-commons.less files
- Renamed the new UI toggle class from _new-ui_ to _ui-refresh_
- Renamed references to the _new ui_ to _v2_

* Created jelly helper to use svg icons

* Fix: restore proper icon for the user on the header

* Fixes for Edge, IE 11 and IE 10

* Improvements on the header and breadcrumbs

- Logo v2 changed and optimized using the svgo frontend https://jakearchibald.github.io/svgomg/
- Refactored the ammonitor insertion code
- Breadcrumbs are no longer capitalized
- Classic logo link no longer stretches past the images
- Fixed classic logo link on IE11
- Updated color of the footer
- Menu items background is also changed when hovering over the menu selector
- Removed copyright notice on top of some files

* Bumped JTH version with the SVG download fix

* Update test/pom.xml

Co-Authored-By: Tim Jacomb <t.jacomb@kainos.com>

* Added a function to check boolean system properties from jelly

* Fix header links and add svg styles for legacy layout

*  Some bug fixing for the new header

- The ui-refresh changes were not properly being enabled with the boolean system property. Added explicit true check on the jelly templates.
- Added an explicit width for the ui-refresh logo because it would mess with the layout

* Update core/src/main/java/hudson/Functions.java

Co-Authored-By: Adrien Lecharpentier <adrien.lecharpentier@gmail.com>

* Do not check the system property on every page render

Co-authored-by: Tim Jacomb <t.jacomb@kainos.com>
Co-authored-by: Adrien Lecharpentier <adrien.lecharpentier@gmail.com>
Co-authored-by: Daniel Beck <1831569+daniel-beck@users.noreply.github.com>

core/src/test/java/hudson/FunctionsTest.java

@@ -43,6 +43,7 @@ import java.util.regex.Pattern;
 import jenkins.model.Jenkins;
 import org.apache.commons.io.IOUtils;
 import static org.junit.Assert.*;
+
 import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -559,5 +560,4 @@ public class FunctionsTest {
             return this;
         }
     }
-
 }