Select: add tests

[bill]

Add tests for the dijit.form.Select widget including:

• api (may already be tested in test_Select.html?)
  • get/set value
  • adding/removing elements
  • destroy removes menu too
• selecting element via mouse
  • click, move, click
  • mouse down, mouse move, mouse up (simple menu only)
  • on a very large list that covers the Select itself, mouse down followed by mouse up shouldn't select anything, need to click (again)
  • click arrow then click blank part of screen to close the Select
• a11y
  • selecting item via keyboard
  • ESC to close list
  • tab index (including skipping over disabled widgets)
• display
  • width of drop down matches width of element, or the widest item in the list, whichever is greater
  • currently selected item is highlighted in drop down list
  • s8 max height throttled at 200px, and using arrow keys scrolls the list
  • drop down with 0 entries appears as empty box (with non-0 height)
• required select will flag itself with yellow icon (or tooltip?) if skipped over

[bill]

(In [22468]) Various cleanup of Select tests:

• add comments
• remove apparently unneeded loadDropDown() calls
• use d.getTestCallback() to reduce code
• put performance tests into separate test group (for clarity)

Refs #10343

[bill]

(In [22470]) Select test updates:

• only run tests when URL is like test_Select.html?mode=test
• add destroy test

Refs #10343

[bill]

(In [22472]) Mouse and keyboard tests for dijit.form.Select, fixes #10343.

[bill]

(In [23485]) On Chrome, the menu doesn't overlap the select (even when there's no room to display the menu either above or below the select) refs #10343