Rename a few scripts to be more consistent.
I'm also starting to feel the urge to bud off `subx run` into its own program,
say tools/emulate_x86. It doesn't really rely on the SubX notation at all.
And then I could rename `subx translate` to `translate_subx_bootstrap`.
Only problem: the commands in the Readme get verbose. But the Readme is
gonna need surgery soon anyway to put translate_mu front and center.