Implement &pin const self and &pin mut self sugars

[frank-king]

This PR implements part of #130494.

It introduces the sugars &pin const self and &pin mut self for self: Pin<&Self> and self: Pin<&mut Self>.

[rustbot]

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[rustbot]

Some changes occurred in src/tools/rustfmt

cc @rust-lang/rustfmt

[compiler-errors]

Please add tests to ensure that this sugar is not usable in #[cfg]'d out code.

[oli-obk]

These changes are more likely to conflict with someone's macro_rules macro out there, so we should probably crater it, too. If there is too much breakage we may hold up on adding this syntax and start with a builtin macro expanding to the same ast nodes that you introduced.