[iOS] Extract debug symbols into separate files (ex: dSYM)

Right now it looks like the default for rustc is to bake debug symbols into the framework. We can extract this into a dSYM file and strip the binaries.

It will require a bit more research to figure out how/if these should be distributed though, as it would ideally be possible for users of the framework to have these symbols uploaded with their apps to Apple. This post has some potentially useful info: https://pspdfkit.com/blog/2020/supporting-xcframeworks/.