[macro] Support deriving certain traits via macro (#2418)

This is intended to specifically support the cryptocorrosion project's
ppv-lite86 and groestl-aesni crates. Currently, these crates rely on
zerocopy's `derive` feature, which has caused long build times for some
dependents such as in [1].

The added macro is `#[doc(hidden)]`, and is only designed to support
ppv-lite86 and groestl-aesni. No semver stability guarantees are made
except that we will support the use cases of those specific crates.

[1] rust-random/rand#1574 (comment)

gherrit-pr-id: I6021fbdc0d1e1e30549da129128e5bc002adcee7

Author: joshlf