Refactor steps

Refactor step definitions:

• brdige_bond_team.py - @fpokryvk !1277 (merged)
• commands.py
• connection.py - @fpokryvk !1271 (merged)
• device.py
• doc.py
• dracut.py
• editor.py
• files.py
• nmtui.py
• prepare.py
• vpn.py - @fpokryvk !1270 (merged)
• service.py - @fpokryvk !1245 (merged)

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If you take some file, crate new issue, and link it to the correct line.

Main goals:

• use nmci.process instead of command
• do not use commands for file processing, use nmci.util functions for work with file.
• use nmci.cleanup in "reversible" steps
• use nmci.util.start_timeout()
• use black formatter
• fix pylint warnings
• use f-strings instead of "%s" or .format() or "..."+"..."