stage2 AArch64: begin transition to MIR

This commit includes the transitions for the following instructions:
- add_immediate
- b
- bl
- blr
- brk
- ldp
- ldr
- ldrb
- ldrh
- mov_to_from_sp
- mov_register
- movk
- movz
- nop
- ret
- stp
- str
- strb
- strh
- sub_immediate
- svc

src/codegen.zig

@@ -88,9 +88,10 @@ pub fn generateFunction(
         .wasm64 => unreachable, // has its own code path
         .arm => return Function(.arm).generate(bin_file, src_loc, func, air, liveness, code, debug_output),
         .armeb => return Function(.armeb).generate(bin_file, src_loc, func, air, liveness, code, debug_output),
-        .aarch64 => return @import("arch/aarch64/CodeGen.zig").generate(.aarch64, bin_file, src_loc, func, air, liveness, code, debug_output),
-        .aarch64_be => return @import("arch/aarch64/CodeGen.zig").generate(.aarch64_be, bin_file, src_loc, func, air, liveness, code, debug_output),
-        .aarch64_32 => return @import("arch/aarch64/CodeGen.zig").generate(.aarch64_32, bin_file, src_loc, func, air, liveness, code, debug_output),
+        .aarch64,
+        .aarch64_be,
+        .aarch64_32,
+        => return @import("arch/aarch64/CodeGen.zig").generate(bin_file, src_loc, func, air, liveness, code, debug_output),
         //.arc => return Function(.arc).generate(bin_file, src_loc, func, air, liveness, code, debug_output),
         //.avr => return Function(.avr).generate(bin_file, src_loc, func, air, liveness, code, debug_output),
         //.bpfel => return Function(.bpfel).generate(bin_file, src_loc, func, air, liveness, code, debug_output),