Perform dockpack push & pull with bollard crate

[TomBurdge]

Changes

• Create non-docker CLI functionality to create a docker image from scratch - using this example.
• Pull and export to directory docker images with bollard.
• Add bollard, tokio, and some other crates to dockpack-core.
• Make dock_pack main function async, so that it can use refactored execute_docker_build function.

Non-Feature Changes/chores

• Add pre-commit hooks.
• Make clippy changes/ignore them (see unsafe clippy lint ignore).

Next Steps

• Use the bollard push API to push the built image to remote registry (gradually building up auth configuration support).
• Small re-factoring to remove use of deprecated components of the bollard API (I think it's non-deprecated in current release, and hence the docs, but depcrecated in the pre-release, which is being used here) - now flagged by clippy.
• Potentially re-factor errors to not be a string - I'd like to get up to speed with using anyhow, which seems pretty standard. Returning just strings on errors got a bit confusing at one point, when developing.

This PR will probably be easiest to review when filtering out the chore: listen to clippy in the git diff (these are mostly formatting/clippy recommended changes).

[TomBurdge]

@maxwellflitton
Is the sync_all method actually needed here?

I found the exact details of what this method is doing a little confusing in the docs.

test_unpack_files_from_image still passes without it. But the method only really checks that the process ends without an error.