Fix non_local_definitions warning caused by derive(displaydoc::Display)

[0x009922]

Description

There are dozens of warnings like this (example CI run):

warning: non-local `impl` definition, they should be avoided as they go against expectation
  --> primitives/numeric/src/lib.rs:65:30
   |
65 | #[derive(Debug, Clone, Copy, displaydoc::Display)]
   |                              ^^^^^^^^^^^^^^^^^^^
   |
   = help: move this `impl` block outside the of the current constant `_DERIVE_Display_FOR_NumericError`
   = note: an `impl` definition is non-local if it is nested inside an item and may impact type checking outside of that item. This can be the case if neither the trait or the self type are at the same nesting level as the `impl`
   = note: one exception to the rule are anon-const (`const _: () = { ... }`) at top-level module and anon-const at the same nesting as the trait or type
   = note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue <https://github.com/rust-lang/rust/issues/120363>
   = note: the derive macro `displaydoc::Display` may come from an old version of the `displaydoc` crate, try updating your dependency with `cargo update -p displaydoc`
   = note: `#[warn(non_local_definitions)]` on by default
   = note: this warning originates in the derive macro `displaydoc::Display` (in Nightly builds, run with -Z macro-backtrace for more info)

[Moses-main]

Hello, assign to me this issue.

[DCNick3]

A proper fix require changes to displaydoc. There is already a PR open, but the maintainer hasn't been responding for two months =(

On our side we can just silence the warning and follow up on it later or use a git ref from this PR.

[nxsaken]

I think it should be fine to proceed with this and leave a TODO comment with a link to yaahc/displaydoc#46. Using the PR version of displaydoc feels like the cleaner solution to me.

[nxsaken]

@Moses-main hi, I'm assigning this issue to you. Let's use the PR version of displaydoc as I described in the comment above. Thank you!

[nxsaken]

@Moses-main hi, are you still planning to complete this?

[Moses-main]

Yes, I'd do something about it.