Cleaned up the paddings of the messaging layout and smart replies

Refactored the code such that the reply icon's inset was substracted
from the overall paddings to make all of them consistent. This
will also help in the future as we don't have to update those
paddings manually anymore.

Test: test all sorts of combinations with Notify
Change-Id: I8c6c9951bc73c88d95cb443c8e618c7adca7ebd3
Fixes: 78441535