Fix usage of JIT_FLAG_CODE_EXEC_ONLY flag. (#33623)

Fix usage of JIT_FLAG_CODE_EXEC_ONLY flag. (#33623)

#19219 didn't convert the JIT flags into options on cfg meaning that code currently checked JIT_FLAG_CODE_EXEC_ONLY never executed. Fix handles the new JIT flag in same way as other JIT flags, converted into bit field on cfg.

With this fix, the following C# method:

```
static double Test()
{
    return 1.0f;
}
```

will now generate the following assembly on amd64, when using MONO_ARCH_CODE_EXEC_ONLY:

```
sub rsp,8
mov r11,qword ptr [180003318h]
movsd xmm0,mmword ptr [r11]
add rsp,8
ret
```

Co-authored-by: lateralusX <lateralusX@users.noreply.github.com>