approach to renaming should be more robust

[trvswgnr]

the current approach to renaming is based on a clever shell script that does text replacement on output of existing commands in the rust toolchain. it's fine for a proof of concept, but ideally we would want more control over exactly what is being renamed and host our own binaries.

this would involve changing the names of relevant commands, then building for multiple targets and hosting the files and using that url in the install script. we'd then need to make a script or program that automates that process.

we can start with the compiler. bear in mind we don't need (or want) to rename every instance of rust to crab, we just want the command, its documentation, and its output to be changed.