This makes location info in defmt logs point to the code calling the macro,
instead of always to fmt.rs as before. Fix works with nightlies
starting with today's, and stable 1.81+.
Fix soundness issue introduced in a previous soundness fix https://github.com/embassy-rs/embassy/pull/2602 .
PeripheralRef must not implement DerefMut itself, but the blanket impl must still require DerefMut. Otherwise
you can create two instances of a driver on the same uart by using `&my_uart`.
if you have `PeripheralRef<'a, AnyPIn>` for pin A, and `AnyPin` (owned) for pin B, you can `mem::swap` them.
so, getting access forever to pin A, just by "sacrificing" pin B
this defeats the point of PeripheralRef, which is if you got a `PeripheralRef<'a, T>` then you're only allowed to use the peripheral for `'a`.
Also some drivers rely on the fact only one instance of a singleton exists for soundness, so this is a soundness fix for those.
