This PR introduces the concept of immutable storage data, used for
[Solidity immutable
variables](https://docs.soliditylang.org/en/latest/contracts.html#immutable).

This is a minimal implementation. Immutable data is attached to a
contract; to keep `ContractInfo` fixed in size, we only store the length
there, and store the immutable data in a dedicated storage map instead.
Which comes at the cost of requiring an additional storage read (costly)
for contracts using this feature.

We discussed more optimal solutions not requiring any additional storage
accesses internally, but they turned out to be non-trivial to implement.
Another optimization benefiting multiple calls to the same contract in a
single call stack would be to cache the immutable data in `Stack`.
However, this potential creates a DOS vulnerability (the attack vector
is to call into as many contracts in a single stack as possible, where
they all have maximum immutable data to fill the cache as efficiently as
possible). So this either has to be guaranteed to be a non-issue by
limits, or, more likely, to have some logic to bound the cache.
Eventually, we should think about introducing the concept of warm and
cold storage reads (akin to EVM). Since immutable variables are commonly
used in contracts, this change is blocking our initial launch and we
should only optimize it properly in follow-ups.

This PR also disables the `set_code_hash` API (which isn't usable for
Solidity contracts without pre-compiles anyways). With immutable storage
attached to contracts, we now want to run the constructor of the new
code hash to collect the immutable data during `set_code_hash`. This
will be implemented in a follow up PR.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Signed-off-by: xermicus <cyrill@parity.io>
Co-authored-by: command-bot <>
Co-authored-by: Alexander Theißen <alex.theissen@me.com>
Co-authored-by: PG Herveou <pgherveou@gmail.com>