Update raw.hpp so that we can serialize and deserialize const types

[greg7mdp]

Resolves #796.

Some types are only set in the constructor and never modified. So they are logically const and could be accessed from multiple threads safely.

Using this would allow us to remove some friend declarations (we use private as a way to prevent unchecked access to non thread-safe members).

Ideally we would make the member type const.
The serialization is what trips us up. I feel that the unpack functions in raw.hpp should accept to unpack const members of structs (logically deserializing to recreate a value which is never modified after creation). Right now we cannot mark non-funadamental types that needs to be serialized const.

Also added a test.

[heifner]

Since we have the time. What about making a pass through the code and making what can be const, const.

[greg7mdp]

Since we have the time. What about making a pass through the code and making what can be const, const.

I started doing that, but it does require a lot of changes through the code. For example most of the block_header_state should be const. But typically we create the empty struct and assign members after the fact (see here for example). Also the finish_next function.

Probably if we want to do this I should create another issue.

[heifner]

I started doing that, but it does require a lot of changes through the code. For example most of the block_header_state should be const. But typically we create the empty struct and assign members after the fact (see here for example). Also the finish_next function.

Probably if we want to do this I should create another issue.

For the large refactor like block_header_state a diff issue makes sense. Any low-hanging fruit you can change? At least one would be nice and show a usefulness of the feature.

[ericpassmore]

Note:start
category: Chores
component: Internal
summary: Update raw.hpp so that we can serialize and deserialize const types.
Note:end

[heifner]

I think remove this blank line or add another comment saying this is only for testing purposes and not thread safe.

[greg7mdp]

removed!

[greg7mdp]

I tried to make thsome members of action const, but I hit the issue that I can't find how to regenerate the tests in unittests/wasm-spec-tests/generated-tests, so I gave up. Please review the PR as-is.