properly handle the off pseudo-level in presence of nested logging directives

[japaric]

this handles nested logging directives like:

$ # NOTE the order of these directives doesn't matter
$ DEFMT_LOG=krate=info,krate::module=off,krate::module::inner=info

by treating the off pseudo-level as a explicit "reject" criteria and checking logging directives
from the innermost one (the one that has more module path segments) to the outermost ones

manually tested with:

fn main() -> ! {
    defmt::info!("main");
    bar::bar();
    bar::inner::inner();

    app::exit()
}

mod bar {
    pub mod inner {
        pub fn inner() {
            defmt::info!("inner");
        }
    }

    pub fn bar() {
        defmt::info!("bar");
    }
}

$ DEFMT_LOG=hello=info,hello::bar=off cargo rb hello
INFO  main

$ DEFMT_LOG=hello=info,hello::bar=off,hello::bar::inner=info cargo rb hello
INFO  main
INFO  inner

[Urhengulas]

Looks good. But I didn't fully understand the the code and mainly checked if the tests make sense.

And I added one question and one change request :)

[Urhengulas]

Why do we compare the module names on the byte-level and not as strings?

[japaric]

at the end we want to do str::starts_with in const context but that method cannot be used in const context so instead we do a byte by byte equality check (see the macro expansion). we cannot index into a str and get a u8 so instead we use [u8] slices

[Urhengulas]

For consistency with std, this should read .to_string.

Suggested change

	pub(super) fn to_str(&self) -> String {
	pub(super) fn to_string(&self) -> String {

[japaric]

bors r=Urhengulas

[bors]

Build succeeded:

• ci