`GenKillAnalysis` has five methods that take a transfer function arg:
- `statement_effect`
- `before_statement_effect`
- `terminator_effect`
- `before_terminator_effect`
- `call_return_effect`
All the transfer function args have type `&mut impl GenKill<Self::Idx>`,
except for `terminator_effect`, which takes the simpler `Self::Domain`.
But only the first two need to be `impl GenKill`. The other
three can all be `Self::Domain`, just like `Analysis`. So this commit
changes the last two to take `Self::Domain`, making `GenKillAnalysis`
and `Analysis` more similar.
(Another idea would be to make all these methods `impl GenKill`. But
that doesn't work: `MaybeInitializedPlaces::terminator_effect` requires
the arg be `Self::Domain` so that `self_is_unwind_dead(place, state)`
can be called on it.)
`on_all_children_bits` has two arguments that are unused: `tcx` and
`body`. This was not detected by the compiler because it's a recursive
function.
This commit removes them, and removes lots of other arguments and fields
that are no longer necessary.
