Notify changes after loading icon in sharesheet

The icon loading inside the sharesheet happens as a separate
async task inside the bindViewHolder. We have seen it taking longer
time in some cases which caused the icon loading to happen after the
bindViewHolder resulting in empty icons being loaded in the
sharesheet for wembley/namaste phone devices. This change introduces a
call to notify observers after the icon loading is done.

Test: Tested on device
Bug: 194886990
Change-Id: Id1752f10ced7877efe5eff90aac6db2bd656f34c