fix: add type hints to blob and bucket

[rinarakaki]

The goal of this PR: to pass pyright google/cloud/storage/blob.py

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Fixes #<issue_number_goes_here> 🦕

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🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
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[andrewsg]

Thank you for your submission, and apologies for the significant delay. We were unable to properly evaluate this for consideration because we were preparing a major overhaul and integration of dependency libraries (the 3.0 branch currently in prerelease as 3.0rc1).

We are unable to integrate this PR as-is right now as we need to prepare an overall strategy that will result in the entire library being covered, but I'd like to spend some time gathering information to prepare that strategy now. Can you tell me about your workflow on how you created this PR, how long it took, and what tools you used?