use craftgit for git operation instead of relying on build-package

[dariuszd21]

What needs to get done

use craftgit, where git client is run as a subprocess with the fallback to the git to ensure backward compatibility.

Why it needs to get done

our snap package will bundle with craftgit which is git client packaged specifically for the craft libraries use.
we should use it in the places where we really on the system git and fallback to the git if it's not a snap or the binary is not available.

[syncronize-issues-to-jira]

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The internal ticket has been created: https://warthogs.atlassian.net/browse/CRAFT-3664.

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