Add tests to `/test` for `CalBERT` and `SiamesePreTrainer`

Add test cases and test configs for the mentioned classes. Create 3 test configurations for each function and store them in a JSON. Load each config in each function and test it one after the other

Start in the /test directory and locate the CalBERT and SiamesePreTrainer class entry points, then inspect any existing test configuration patterns. Create or identify the JSON containing three configurations for each class, load each configuration in turn, and run the test suite; done means all six configurations are exercised successfully.

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