Now that it will be used by four VCL plugins, move its code into
the common VCL library. The none-XAccessibility, none-UNO version
used on Windows needs much more work to function with various
widgets (including some API refactoring IMHO).
(see ImplHandleSalSurroundingTextRequest and friends).

Change-Id: I0fdf72336a66fc578b18b1edc8f8627d5dfdc57f
Reviewed-on: https://gerrit.libreoffice.org/72364
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>