Clicking on a test name on the new flakiness dashboard should add a new test pane

Clicking on a test name on the new flakiness dashboard should add a new test pane
https://bugs.webkit.org/show_bug.cgi?id=123194

Reviewed by Simon Fraser.

Added a new click handler on each test name inside the builder test view add a new test pane.
Moved the old trac link to a right-arrow inline SVG icon.

Also tweaked the style so that the builder test view looks different from other test panes.

* index.html:
(TestResultsView._urlFromTest): Extracted from TestResultsView._linkifiedTestName.
(TestResultsView._populateBuilderPane): Fetch the test when its name is clicked.
Added a circled right arrow for the old trac link.
* main.css: Tweaked the style to move the rounded border around the builder test view to be
around the form controls to clearly differentiate it from a regular test pane.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@157880 268f45cc-cd09-0410-ab3c-d52691b4dbfc