Prepare for 0.12.0-pre.8 release

[afterdusk]

0.12.0-pre.8 (August 23, 2024)

• Fixed a bug in key history API that occurs when a proof is being generated while a transaction is being committed
• Updated test vectors to the latest version

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.03%. Comparing base (3ce5335) to head (a7e86dc). Report is 20 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #451 +/- ## ========================================== - Coverage 88.61% 88.03% -0.58% ========================================== Files 39 38 -1 Lines 9109 8283 -826 ========================================== - Hits 8072 7292 -780 + Misses 1037 991 -46 ```

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