[FIX] sap.m.Select: TAB handling added
[FIX] sap.m.Select: TAB handling added

Due to the lack of such handling methods, the sap.m.Select caused
inpredictable behaviour such as:

- When you open the Select using the Space key and then press
  TAB immediatly, the Select would stay open with fake focus
  over one of the items, when in reality, the focus would be on
  the next focusable element. If you pressed TAB several times
  until you reach the Select again, the TAB would then go through
  the items inside, while keeping the scroll from the initial opening
  while having another on the currently focused item.

The fix provides methods for tab forward/backwards, which close the list
if it was opened, while keeping the newly selected value in the meantime
(if any).

Change-Id: Ib18b219e2af358b82a0f2c1a09dff322f2f276cb
BCP: 1780356162

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