Bytes storage

[cicdw]

Thanks for contributing to Prefect!

Please describe your work and make sure your PR:

• adds new tests (if appropriate)
• updates CHANGELOG.md (if appropriate)
• updates docstrings for any new functions or function arguments, including docs/outline.toml for API reference docs (if appropriate)

Note that your PR will not be reviewed unless all three boxes are checked.

What does this PR change?

Back by popular demand, it's Bytes storage.

Why is this PR important?

For local testing, we needed something less ephemeral than Memory and still something that doesn't rely on file system storage.

[codecov]

Codecov Report

Merging #961 into master will increase coverage by 0.03%.
The diff coverage is 100%.