[llvm-c] Expose debug support for LLJIT in Orc C-API bindings (#73257)

Allow C-API users to debug their JITed code via the GDB JIT Interface.

This is currently supported on ELF and MachO based platforms. On
other systems `LLVMOrcLLJITEnableDebugSupport()` returns an error.

This patch adds a new C-API header `LLJITUtils.h`, which can host
further advanced JIT features in the future. Using the header requires
linking against LLVMOrcDebugging.