Set admin password on cluster bootstrap via PICODATA_ADMIN_PASSWORD env var

Summary

With the current implementation you can set up a password for admin and connect remotely

Set PICODATA_ADMIN_PASSWORD environment variable initialized with password in your shell

And connect with picodata connect <ADDRESS> --user admin

• Close #702 (closed)
• Cherry-pick to: none
• Docs follow-up: docs#315 (closed)

Closes #702 (closed)