[llvm] Implement S_INLINEES debug symbol (#67490)

The `S_INLINEES` debug symbol is used to record all the functions that
are directly inlined within the current function (nested inlining is
ignored).

This change implements support for emitting the `S_INLINEES` debug
symbol in LLVM, and cleans up how the `S_INLINEES` and `S_CALLEES` debug
symbols are dumped.