Auto merge of #95548 - rcvalle:rust-cfi-2, r=nagisa

Auto merge of #95548 - rcvalle:rust-cfi-2, r=nagisa

Add fine-grained LLVM CFI support to the Rust compiler

This PR improves the LLVM Control Flow Integrity (CFI) support in the Rust compiler by providing forward-edge control flow protection for Rust-compiled code only by aggregating function pointers in groups identified by their return and parameter types.

Forward-edge control flow protection for C or C++ and Rust -compiled code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code share the same virtual address space) will be provided in later work as part of this project by identifying C char and integer type uses at the time types are encoded (see Type metadata in the design document in the tracking issue https://github.com/rust-lang/rust/issues/89653).

LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e., -Clto).

Thank you again, `@eddyb,` `@nagisa,` `@pcc,` and `@tmiasko` for all the help!