Clean up controller signals to improve abstraction

[linh2931]

Currently controller signals an all-purpose block_state_legacy_ptr for accepted_block_header, accepted_block, and irreversible_block. block_state_legacy_ptr is passed across functions, hiding actual parameters a function needs. Over 40 files depend on block_state_legacy.hpp.

This PR

• Changed to signal types which are only required.
• Changed function interface to use exact parameters instead of one-for-all block_state_legacy_ptr and updated implementation
• Updated tests
• Removed unused signals pre_accepted_block, accepted_transaction, and bad_alloc.

Those changes

• help make Instant Finality coding simpler by removing the need to signal variant types,
• reduce abstraction leakage,
• reduce the overall codebase dependency on to-be-obsolete block_state_legacy_ptr by removing the majority uses of it.

Resolved #1957

[greg7mdp]

I would create a type:
using block_signal_params_t = std::tuple<const signed_block_ptr&, const block_id_type&, const signed_block_header&, uint32_t>;

And use the same type for all 3 signals.

[linh2931]

Thanks. Will change.

[heifner]

Why signed_block_header. When is signed_block_header != static_cast<signed_block_header>(*signed_block_ptr) ?

[heifner]

I see no reason for uint32_t block_num. The user can just use signed_block_ptr->block_num(). The id is included because calculate_id() is expensive, but block_num() I think is efficient enough we don't need to include it in the signal.

[linh2931]

I decided to use signed_block_header and block_num explicitly for calling out parameters required by signal clients and for easier review to make sure nothing is missed during the changes. But we need to strike some balances between the number of parameters to signal and abstraction leakage.

[linh2931]

7c4ca8a