Make sh_binary a HostToolProvider

sh_binary modules should implement HostToolProvider so that they
can be used in genrules.  Install the script and then return
the installed path.

Also remove the unused SourceFilePath method.

Bug: 122332855
Fixes: 146496647
Test: m checkbuild
Change-Id: I191ce4eef1d50ac0b6a296b819feec6d6a18e753