There is a weak convention in the ecosystem that `IterFoos` is an
iterator yielding items of type `Foo` (e.g. `bitflags` `IterNames`,
`hashbrown` `IterBuckets`), while `FooIter` is an iterator over `Foo`
from an `.iter()` or `.into_iter()` method (e.g. `memchr` `OneIter`,
`regex` `SetMatchesIter`). Rename `IterRange`, `IterRangeInclusive`, and
`IterRangeFrom` to `RangeIter`, `RangeInclusiveIter`, and
`RangeInclusiveIter` to match this.
Tracking issue: RUST-125687 (`new_range_api`)
