Update cli UX

Picodata follow-up

Updates in picdata admin and picodata connect CLI:

1. EOF is a delimiter for files
2. New inner_prompt for command that is incomplete (command is incomplete until delimiter is specified)
3. Special commands can be called without delimiter

See the screenshots in the comments

• Follow-up for picodata!1390
• See also picodata#1059, picodata#1065, picodata#1067
• Doc pages to change: everywhere