[INTERNAL] sap.m.Slider: add renderer writeHandleTooltip hook
[INTERNAL] sap.m.Slider: add renderer writeHandleTooltip hook

- add renderer .writeHandleTooltip() hook method to make possible to
override the tooltip of the handle in subclasses

Change-Id: I4a0f9a1e59d07778cbf4c19a6ab27dc4ba626e90

cschuff/openui5,olirogers/openui5,olirogers/openui5,nzamani/openui5,cschuff/openui5,SQCLabs/openui5,SAP/openui5,SAP/openui5,nzamani/openui5,SAP/openui5,SQCLabs/openui5,olirogers/openui5,SAP/openui5,cschuff/openui5,nzamani/openui5,SQCLabs/openui5