* Use macros for more division/array checks
This commit moves over more array accesses to the `i!` macro to avoid
bounds checks when debug assertions are disabled. This is surfaced from
rust-lang/compiler-builtins#360 where recent changes in codegen units
has caused some bounds checks to not get elided in release mode. This
also adds a `div!` macro to work around rust-lang/rust#72751.
* Don't test/bench our shim crate
It's not intended to run all our tests
