x64: clean up `br_if(op(a, b))` codegen

Follow up issue to https://github.com/bytecodealliance/wasmtime/pull/11122

The semantics of `br_if` are such that we branch to the consequent on a non-zero condition value and the alternative on a zero condition value. Often we are emitting x64 instructions to to the `op` and then explicitly test whether the result is zero or non-zero and branch accordingly. However, for many `op`s we can instead just do some kind of test/compare on `a` and `b` directly, instead of the `op` and then a non-zero test.

For example given

```wat
local.get 0
local.get 1
i32.or
if ;; label = @1
call 0
else
call 1
end
```

we currently emit the comparison as

```asm
00000019 0b d1 or edx, ecx
0000001b 85 d2 test edx, edx
0000001d 0f 85 15 00 00 00 jne 0x38
...
```

but we should be able to do something like

```asm
or edx, ecx
je 0x38
...
```

instead.

I think that we can add special cases for `br_if(op(a, b))` for all `op`s in `{iadd, isub, bor, bxor}`. Maybe more. (Note that we already have a `br_if(band(a, b))` special case).

Note that doing this might require some additional refactorings in the x64 assembler library and its ISLE constructor generation: https://github.com/bytecodealliance/wasmtime/pull/11122#issuecomment-3001204011