Use `thiserror` for errors

[fjarri]

We are currently using displaydoc for Display derivations and manual From impls for error conversion. thiserror can handle that - once dtolnay/thiserror#304 is in so that it supports no-std.

[fjarri]

thiserror 2.0 has been released, with no-std support. This issue is unblocked.

[fjarri]

Also worth considering here: https://docs.rs/error-stack, to attach context-specific info to errors. It is additive with thiserror.