High level ELF write API

We're currently using two libraries for patching ELF files (https://github.com/PyO3/maturin/pull/2932): Goblin for "linting" build artifacts and reading the RPATH, where it has convenient high-level functions, and object for adjusting RPATH/SONAME/etc. through [arwen](https://github.com/nichmor/arwen). I've been looking at the [faerie example](https://github.com/m4b/faerie/blob/04ea1211a677457b331e3f97ec7131dad3dfb655/src/elf.rs#L784-L1041) for writing ELF files, but it seems there's no typed, safe ELF write API, with which we could replace parsing with both goblin and object with using goblin specifically for ELF files.

Start by reading the faerie ELF example at src/elf.rs lines 784-1041, then review how Goblin and object are currently used for ELF linting, RPATH reading, and writing through arwen. Done would mean a defined, typed, safe high-level ELF write API capable of replacing the described Goblin/object workflow.

Written by the indexing model from the issue text.