feat: add requires_command guard sentinel and check_preconditions() hook#1647

Fizzadar merged 2 commits intopyinfra-dev:3.xpyinfra-dev/pyinfra:3.xfrom

maisim:feat/fact-preconditions-and-requires-commandmaisim/pyinfra:feat/fact-preconditions-and-requires-commandCopy head branch name to clipboard