Add proper name mangling for pattern types

[oli-obk]

requires adding demangler support first rust-lang/rustc-demangle#81

needed for #136006 (comment) as otherwise we will have symbol collisions

[rustbot]

r? @petrochenkov

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[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[petrochenkov]

@bors r+

[bors]

📌 Commit 739e899 has been approved by petrochenkov

It is now in the queue for this repository.