Align number implementations to 256 bits

[clearloop]

Describe the feature

we only can do static type checks while compiling since the stack item of solidity is 256 bits, so whatever optimize the types or not doesn't matter to EVM, but still needs these types

• i128
• u128
• i256
• u256

Solution

Need an external library to implement these, mb defined in zink/numbers

---

for u256 operations, we can use host functions like ("zink", "u256_add"), etc, do it in EVM for saving space in WASM:

• u256::Zero -> ("zink", "u256_zero")

[clearloop]

in favor of #156