access_control.md: address formal requirements

• access_control.md: track formal requirements
• access_control.md: extend db_user with commands
• access_control.md: revise user_management
• access_control.md: revise tables_access
• access_control.md: revise proc_access

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• Follow-up for !380 (merged), #209 (closed)
• Part of picodata#340
• Target branch: main
• Changes should be cherry-picked to 24.2: yes
• Staging:
  • https://docs.binary.picodata.io/picodata/rosik_access_control/tutorial/access_control/#db_user
  • https://docs.binary.picodata.io/picodata/rosik_access_control/tutorial/access_control/#user_management