Rollup merge of #58553 - scottmcm:more-ihle, r=Centril

Use more impl header lifetime elision

Inspired by seeing explicit lifetimes on these two:

- https://doc.rust-lang.org/nightly/std/slice/struct.Iter.html#impl-FusedIterator
- https://doc.rust-lang.org/nightly/std/primitive.u32.html#impl-Not

And a follow-up to https://github.com/rust-lang/rust/pull/54687, that started using IHLE in libcore.

Most of the changes in here fall into two big categories:

- Removing lifetimes from common traits that can essentially never user a lifetime from an input (particularly `Drop`, `Debug`, and `Clone`)

- Forwarding impls that are only possible because the lifetime doesn't matter (like `impl<R: Read + ?Sized> Read for &mut R`)

I omitted things that seemed like they could be more controversial, like the handful of iterators that have a `Item: 'static` despite the iterator having a lifetime or the `PartialEq` implementations [where the flipped one cannot elide the lifetime](https://internals.rust-lang.org/t/impl-type-parameter-aliases/9403/2?u=scottmcm).

I also removed two lifetimes that turned out to be completely unused; see https://github.com/rust-lang/rust/issues/41960#issuecomment-464557423

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index 1f3b264c414..543973ab991 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -399,7 +399,7 @@ impl<'a> Iterator for SplitPaths<'a> {
 }
 
 #[stable(feature = "std_debug", since = "1.16.0")]
-impl<'a> fmt::Debug for SplitPaths<'a> {
+impl fmt::Debug for SplitPaths<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("SplitPaths { .. }")
     }