[Breaking] Update to bitflags 2.x

[GnomedDev]

Gets rid of this old duplicate dependency in my dep tree.

[whitequark]

Does defmt no longer provide a derive macro?

[GnomedDev]

bitflags 2.x swapped the internals of each bitflag type from just a newtype around the integer to a newtype around a private newtype. This means that derives that just try to touch the inner value can't work, hence having to make our own macro to implement formatting the bits.

[whitequark]

Thanks. @Dirbaio what do you think about the macro? it feels a bit heavyweight but maybe that's just me.

[GnomedDev]

I can change the macro to be separate and not replace the bitflags invocation, if that would be preferred, as in

bitflags::bitflags! {
	pub struct Flags: u8 {
		...
	}
}

impl_bitflags_defmt!(Flags);