Make all the important symbols from .core in the pybit7z namespace

[msclock]

From https://www.reddit.com/r/Python/comments/1hq8tx8/comment/m4ofk8l/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

[msclock-bot]

🎉 This issue has been resolved in version 0.2.4 🎉

The release is available on GitHub release

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