CHANGELOG for 0.12.0 release

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Summary: changelog

Differential Revision: D62405336

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This pull request was exported from Phabricator. Differential Revision: D62405336

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Codecov Report

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

Project coverage is 99.98%. Comparing base (509bccc) to head (457d162). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2522 +/- ## ======================================= Coverage 99.98% 99.98% ======================================= Files 193 193 Lines 17010 17010 ======================================= Hits 17007 17007 Misses 3 3 ```

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This pull request was exported from Phabricator. Differential Revision: D62405336

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D62405336

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D62405336

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D62405336

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This pull request has been merged in pytorch/botorch@85364681a84ac2276b423fe575f33db1e1df311b.