This reverts the toolbarmanager.cxx part of
38839ae1 ("Remove the
ability to set tooltips in the toolbar xml files").

It is true that tooltips can't be set in xml files,
but toolbars can also be created/modified via the
UIConfigurationManager and LayoutManager APIs,
e.g. the test doc of i#105626 .

Change-Id: Ida1559e61e7fd9bd6dcdd7b7159bc5efe070c721