* Add prompt caching
* remove anthropic-version from extra_headers
* change supports_prompt_caching method to attribute
* change caching strat and log cache statistics
* add reminder as a new message to fix caching
* fix unit test
* append reminder to the end of the last message content
* move token logs to post completion function
* fix unit test failure
* fix reminder and prompt caching
* unit tests for prompt caching
* add test
* clean up tests
* separate reminder, use latest two messages
* fix tests
---------
Co-authored-by: tobitege <10787084+tobitege@users.noreply.github.com>
Co-authored-by: Xingyao Wang <xingyao6@illinois.edu>
Co-authored-by: Engel Nyst <enyst@users.noreply.github.com>