Prepare release 0.8.0

[j6k4m8]

Summary

• document backend correctness, performance, dialect, and test changes since 0.7.0
• bump package and runtime versions to 0.8.0
• update the lockfile package metadata

[codspeed-hq]

Merging this PR will not alter performance

✅ 17 untouched benchmarks

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_{Comparing release/0.8.0 (23e8292) with master (a9b7a52)}