Use rust-based coverage tools rather than tarpaulin

[bfjelds]

Migrate away from tarpaulin as code-coverage in favor or compiler-driven coverage tool built into rust.

More description here

This may lead to more accurate coverage numbers.

[bfjelds]

i'm not sure, but using this system might allow for coverage numbers to cover both unit tests and e2e tests:

https://stackoverflow.com/questions/3166198/with-gcov-is-it-possible-to-merge-to-gcda-files