Auto merge of #66279 - cjgillot:hashstable, r=Zoxc

Use proc-macro to derive HashStable everywhere

Hello,

A second proc-macro is added to derive HashStable for crates librustc depends on.
This proc-macro `HashStable_Generic` (to bikeshed) allows to decouple code and strip much of librustc's boilerplate.

Still, two implementations `Span` and `TokenKind` require to be placed in librustc.
The latter only depends on the `bug` macro. Advise welcome on how to sever that link.
A trait `StableHasingContextLike` has been introduced at each crate root,
in order to handle those implementations which require librustc's very `StableHashingContext`.

This overall effort allowed to remove the `impl_stable_hash_for` macro.

Each commit passes the `x.py check`.
I still have to double check there was no change in the implementation.

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