feat: multiline input

Summary

Added support of setting custom delimiter:

• picodata admin (lua/sql mode)
• picodata connect

Fixed problem with unsaved history for Lua mode. Treating empty lines as queries.

The following useful use case of picodata connect/admin is available:

picodata admin admin.sock < your_file,

where your_file may contain several queries. Configure custom delimiter via '\set delimiter ;' at the beginning of your script.

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• Close #516 (closed)
• Cherry-pick to: none
• Docs follow-up: docs#307 (closed)