Add `contractID` to contract state (aka `rootState[contractID]`)

[corrideat]

Problem

There are two ways that Chelonia can work on a contract. In many functions we use the contractIDOrState convention that allows passing in a contract ID (in which case, we do rootState[contractID]), or we allow the state to be passed in directly.

Depending on use case, one or the other might be more appropriate. However, if these selectors or functions are being called from a contract, the one taking the state directly often is the more adequate choice, and this state is a different object than the state at the root.

Mostly for logging, we would like to have access to the contractID when a state is passed. We could pass the ID as a parameter, but since it's not possible to check its correctness, there's a chance that it might be wrong.

A more robust and DRYer solution is to include the contractID in the state (e.g., as _vm.contractID), with some guards that ensure its immutable.

Solution

Add _vm.contractID to the state.