[bug#56037] [PATCH] gnu: Update hexyl to 0.10

[antlers]

Hi! Thanks for putting these together. I've been able to use them
while packaging another program for personal use, and while they're
working great, we might have a few things to polish before they're
clean enough to merge; in particular, I noticed some low hanging
warnings when running `guix lint`.

The package list as I collected it goes like so:
```
make; ./pre-inst-env guix lint \
    hexyl rust-clap rust-clap-derive rust-clap-lex rust-const-format \
    rust-const-format-proc-macros rust-trycmd rust-textwrap rust-libtest-mimic \
    rust-snapbox rust-snapbox-macros rust-similar rust-toml-edit rust-kstring
```

If you've got time to take a look, I'd love to see these patches flow
upstream, and if you don't, I could probably make time to give it a go
myself within the next ~two weeks-- if you wouldn't mind c:
Disclaimer being that I'm very new to Guix myself, and have no
experience with Rust at all-- but figure that shouldn't impede
polishing minor update patches.