Datepicker: Abstract mouseover logic to avoid explicit event trigger

The reliance on `.mouseover()` caused an issue in some circumstances
(see #5816). The removal of `.mouseover()` broke keyboard navigation
(see #10319).

Fixes #10319
Closes gh-1290
Widget: Improve performance of cleanData method

Fixes #9546
Closes gh-1291
Position: Support positioning within document with jQuery 1.6.x

Fixes #10071
Closes gh-1294
Resizable: Fix size/position changes in resize event

Fixes #10351
Closes gh-1292
Autocomplete: ESCAPE should not change content of a MultiLine

Fixes #9790
Closes gh-1190
Autocomplete: Fix styling for combobox demo

Fixes #10059
Selectmenu: Properly set width for button

Fixes #10145
Closes gh-1296
Selectmenu: Preserve text selection when interacting with the widget

Fixes #10144
Closes gh-1295
Selectmenu: Don't check menu width in width option tests
Selectmenu: Remove unused var in test
Core: Clean up selector tests
Core: Fix focusable detection for image maps

The attribute selector requires quotes to be valid, but only new (unreleased)
Sizzle has this requirement.
Core: Ensure forms in tests have some actual content

Empty forms have no height, so they're considered hidden in jquery-git as of
jquery/jquery@10399ddcf8a239acc27bdec9231b996b178224d3
Tests: Fix composite tests
Tests: Whitespace
Resizable: Fix containment calculation with relative parent

Remove an incorrect fix introduced in 47cd5b6f that causes
width calculations to be incorrect once the correct fix
was introduced in c03cb807

Fixes #10140
Resizable: Fix containment width with relative parent.

Refs #10140
Closes gh-1303
Resizable: account for padding & border in grids.

Fixes #10437
Tests: Fix TestSwarm submissions for old jQuery
Authors: Update