Sema: catch invalid asm input operands

[wooster0]

$ zig-out/bin/zig test test/cases/compile_errors/non_sized_asm_input_operand.zig
test/cases/compile_errors/non_sized_asm_input_operand.zig:4:23: error: input operand of type 'type' is not sized
        : [_] "{al}" (u8),
                      ^~
test/cases/compile_errors/non_sized_asm_input_operand.zig:12:22: error: input operand of type 'type' is not sized
          [_] "{x}" (void),
                     ^~~~
test/cases/compile_errors/non_sized_asm_input_operand.zig:19:22: error: input operand of type 'type' is not sized
        : [_] "{x}" (enum {}),
                     ^~~~~~~

I don't know if disallowing non-sized types is the best solution because for example RISC-V has a zero register that is hardwired to zero so : [x0] "{x0}" (@as(u0, 0)), in a way could be valid but u0 is non-sized so it won't work. At the same time though you can argue that anything that isn't sized can't actually be in a register.

Fixes #7843 (wasn't an issue with just stage1 btw, stage2 too segfaults without this patch)