add onFocus valueText to GFLBMassControl, add on demand onFocus update with updateOnFocusAriaValueText, update on focus valuetext when force changes, https://github.com/phetsims/gravity-force-lab-basics/issues/96
add onFocus valueText to GFLBMassControl, add on demand onFocus update with updateOnFocusAriaValueText, update on focus valuetext when force changes, https://github.com/phetsims/gravity-force-lab-basics/issues/96

phetsims/sun,phetsims/sun,phetsims/sun