[rust] Use apple-flat-package crate to extract PKG files (#13740)

* [rust] Use apple-flat-package crate to extract PKG files

* [rust] Bump rules_rust to v0.40.0

* [rust] Remove version from toolchain register

* [rust] Remove crate in unit test config

* [rust] Remove srcs from run test setup

* [rust] Include edition in rust test block

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Co-authored-by: Diego Molina <diemol@users.noreply.github.com>