Causes deprecation warnings.
Most of this code is copy-pasted from OO.ui.SearchInputWidget.
Bug: T148471
Change-Id: I81d52ba938a8b90c5d2c173f1f2682d9e3300e43
For consistency with how normal OOjs UI widgets behave.
Only one usage outside of HTMLForm needed updating. There
are no usages in extensions in Gerrit.
Change-Id: I9b5de86307a13ca7355b7541e8683e4d6a10431f
SearchInputWidget is similar to a TitleInputWidget, but doesn't has
a visible loading indication, doesn't highlight the first result and
uses the opensearch api endpoint for suggestions, instead of
prefixsearch.
Extra points:
* Improve documentation of mw.widgets.TitleInputWidget's configuration
option validateTitle
Bug: T118443
Change-Id: I8b8098041fe2971389fa908d007d2e77255829ec