Amend unknown bitflag contain check

[atlv24]

Connections
I may have broken this in #6644 but im not fully certain. This should work and be clearer anyways.

Description
bitflag equality check may be truncating to known bits before comparing

Testing
intuition :| im not sure if we have test coverage of these failure cases. we may want to add some, im not sure how to though.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[nical]

(I am not opposed to this change but) I did a quick and dirty test and it looks like flags | Flags::all() != Flags::all() does what we want (it does not truncate the bits) with the latest version of the bitflags crate.

[atlv24]

oh, thanks! i just got worried, its good to know i didnt mess it up. tried reading the source and didnt find where Eq was implemented

[cwfitzgerald]

I feel like this could use a generic utility in an extension trait for all T: Flags, so the code would read flags.contains_invalid_bits() or smth

[cwfitzgerald]

Actually this should be able to be spelled flags.contains(T::all()), which is clear enough. Nope, it would have to be T::all().intersects(flags) or something - probably better to have it as a dedicated function so we don't have to remember which arcane bit thing we need to use.

[atlv24]

i tried the flags.intersects(!T::all()), it doesnt work. intersects is truncating i think

[atlv24]

bitflags/bitflags#425