Switch to install_wheel in InstallRequirement
Switch to install_wheel in InstallRequirement

This removes one of usages of the overloaded `source_dir` member.

We know the local_file_path must be set at this point because it is set
in the only 3 places that wheels are added to InstallRequirement.

pfmoore/pip,xavfernandez/pip,pypa/pip,xavfernandez/pip,xavfernandez/pip,sbidoul/pip,pradyunsg/pip,pfmoore/pip,sbidoul/pip,pypa/pip,pradyunsg/pip