Client/voting: improve how it checks voting rights

This MR adds a new RPC to check whether a delegate is in the voting listing or not /chains/<chain_id>/blocks/<block>/context/delegates/<delegate_pkh>/voting_info. Then, this MR changes how tezos-client checks voting right: instead of downloading the full listings it now query the node with the new RPC.

Manually testing the MR

dune exec tezt/tests/main.exe -- --color --verbose --file voting.ml

Checklist

• N/A Document the interface of any function added or modified (see the coding guidelines)
• N/A 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).