feat: Apply numerous API fixes for LLVM v19

[Sightem]

This PR addresses multiple compilation errors, linker failures, and runtime crashes encountered while porting the z80 backend to LLVM v19. The changes span the z80 target implementation as well as minor fixes to core LLVM headers required for a successful build

Known Issue:

int global_result = 0;

int main(void) {
    volatile int x = 10;
    for (int i = 0; i < 5; ++i) {
        global_result += x;
    }
    return global_result;
}

from what I can tell, global_result += x now fails with a "cannot select" error. This seems to be because the backend currently lacks GlobalISel patterns for general register to register addition (only the INC/DEC optimization is implemented)

[adriweb]

Well considering I wasn't able to test v19 because of tablegen issues in the first place, if this gets us closer, it's a win.