the original rb_wasm_setjmp implementation always unwinds to the root
call frame to have setjmp compatible interface, and simulate sjlj's
undefined behavior. Therefore, every vm_exec call unwinds to main, and
a deep call stack makes setjmp call very expensive. The following
snippet from optcarrot takes 5s even though it takes less than 0.3s on
native.

```
[0x0, 0x4, 0x8, 0xc].map do |attr|
  (0..7).map do |j|
    (0...0x10000).map do |i|
      clr = i[15 - j] * 2 + i[7 - j]
      clr != 0 ? attr | clr : 0
    end
  end
end
```

This patch adds a WASI specialized vm_exec which uses lightweight
try-catch API without unwinding to the root frame. After this patch, the
above snippet takes only 0.5s.