* extensions: Make naming and layout consistent across all extensions
breaking change:
- some extensions were exposing `instance()` instead of `device()`
includes:
- renaming function pointer member to `fns`
- moving `name()`, `fp(`), `device()`/`instance()` functions at end of file
- adding missing `device()`/`instance()` functions
see https://github.com/MaikKlein/ash/pull/493
* debug_marker: Remove unneeded `device` from `debug_marker_set_object_name()`
* extensions: Remove unneeded `instance` and `device` struct members and functions
* extensions: renamed all `fns` fields to `fp` to match `pub fn fp()` getter
Fixes https://github.com/MaikKlein/ash/issues/354
`io::Read::read_exact` does not receive `MaybeUninit` memory and a trait
implementation can possibly read from our uninitialized vector without
`unsafe`, which is UB. As there is no proper solution to this problem
yet (see linked issue), our safest bet is to just take the perf-hit and
zero-initialize this vector.
