Remove ToolBarLayoutManager::implts_createUIElement()

There is no need for this function, merge it into createUIElement.
This really helps when I'm looking at a backtrace in gdb.

Change-Id: I005b5161eb2cc8acf509ae7ba4e41186969904d1
Reviewed-on: https://gerrit.libreoffice.org/9309
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>