Rollup merge of #155684 - bushrat011899:blanket_io_seek_for_ref, r=jhpratt

Generalize IO Traits for `Arc<T>` where `&T: IoTrait`

ACP: rust-lang/libs-team#755
Tracking issue: rust-lang/rust#154046
Related: rust-lang/rust#94744

## Description

After experimenting with rust-lang/rust#155625, I noticed `Seek` and `SeekFrom` can almost be moved to `core::io`. Unfortunately, the implementation of `Seek` for `Arc<File>` is a blocker for such a move, since `Arc` is not a fundamental type. This PR attempts to resolve this potential blocker by replacing the implementation with a more general alternative. An internal trait `IoHandle` has been added which types can implement to opt-in to `Read`/`Write`/`Seek` implementations for `Arc<Self>` as long as `&Self` implements said trait. Note that `BufRead` is excluded as the signature for `fill_buf` would require returning from a temporary.

Since this "blanket" implementation only applies to a single type which already implements the same traits, I believe this should have no user-facing impact.

If this PR was merged, rust-lang/rust#134190 could be replaced with a 2 line PR:
```rust
impl IoHandle for TcpStream {}
impl IoHandle for UnixStream {}
```
Likewise for any other types, a table of which can be found [here](rust-lang/libs-team#504 (comment)). This is out of scope for this PR to avoid the need for an ACP.

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## Notes

* See [this comment](rust-lang/rust#154046 (comment)) for further details.
* No AI tooling of any kind was used during the creation of this PR.

Author: jhpratt