Support factory pattern in the core

There's feedback coming from the contract developers that the factory pattern is something they want to use. For example, a common scenario might be that a contract could own an ERC20 token with additional custom logic.

Technically we do support it on the EE, but we never introduced necessary tests, and it was never introduced into the core as a supported feature.

At a minimum, we need to implement tests for a session code that will deploy contract A (aka factory contract) with entrypoints marked as `group(vec![])` (essentially can't be called) and a contract entry point that creates a contract B (new contract) with the same set of entrypoints but different entry point access.

It will be worthwhile to discuss the possibility if the factory contract needs to have symbols in the WASM present, or we can somehow create those reserved entrypoints on the fly without the burden on developers to remember to create all possible symbols in advance.