refactor: remove Lua API functions

Summary

• refactor: remove Lua API pico.create_role
• refactor: remove Lua API pico.drop_role
• refactor: remove Lua API pico.create_user
• refactor: remove Lua API pico.drop_user
• refactor: remove Lua API pico.grant_privilege
• refactor: remove Lua API pico.revoke_privilege
• refactor: remove Lua API pico.change_password
• refactor: remove Lua API pico.raft_get_index
• chore: bump LUA_API_VERSION
• chore: update CHANGELOG.md
• chore: proofread CHANGELOG.md

Changes:

• pico.change_password — ALTER USER
• pico.create_role — CREATE ROLE
• pico.create_user — CREATE USER
• pico.drop_role — DROP ROLE
• pico.drop_user — DROP USER
• pico.grant_privilege — GRANT
• pico.raft_get_index — .proc_get_index
• pico.revoke_privilege — REVOKE

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• Benefits #432 (closed)
• Part of docs#263
• Cherry-pick to: none
• Docs follow-up: docs#322 (closed)
• See also: Google Sheets - RPC API