Resolve "Snoop: separate Generated_cost module in michelson_v1_gas.ml of protocol"

Context

Resolves #3736 (closed) (also #3530 (closed) as this is included within).

Part of the milestone %(OKR 2022Q3 - 4.2) - Gas effort: Codegen

This MR splits Generated_costs module written in src/proto_alpha/lib_protocol/michelson_v1_gas.ml into two files; michelson_v1_gas_cost.ml and michelson_v1_gas_cost_generated.ml towards the automatic generation of the gas cost module.

• michelson_v1_gas_cost_generated.ml will be auto-generated by the snoop in future MRs. In this MR, this is the part of the previous michelson_v1_gas.ml without modification.
• michelson_v1_gas_cost.ml includes michelson_v1_gas_cost_generated.ml and also contains some functions that cannot be generated by the current snoop.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR