[PAC][lldb][Dwarf] Support `__ptrauth`-qualified types in user expressions (#84387)

Depends on #84384 and #90329

This adds support for `DW_TAG_LLVM_ptrauth_type` entries corresponding
to explicitly signed types (e.g. free function pointers) in lldb user
expressions. Applies PR https://github.com/apple/llvm-project/pull/8239


from Apple's downstream and also adds tests and related code.

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Co-authored-by: Jonas Devlieghere <jonas@devlieghere.com>