Fix: u128 deser errors

[gluax]

Motivation

Fix the deserialization errors caused by recent changes

Explanation of Changes

List of changes:

1. Make a Uint128 type for the not cosmwasm side. That can correctly serialize and deserialize.
2. Add lots of quality of life/ergonomics on said type.
3. Change factory to return top-level ExecuteMsg, this fixes some errors on the overlay side and makes it cleaner.
4. Adds new tests to test ser and deser for types.

Testing

Adds new tests old, tests pass.

Related PRs and Issues

N/A

[FranklinWaller]

Like the tests :)