Add a unittests bash script for easier testing

[dylan-apex]

When running unit tests, they are reliant on only having test, a2a, and eval installed, whereas the default during development is to do uv sync --all-extras and this is required for the autoformat script (isort and pyink must be installed).

I propose adding a new script unittests.sh that will automatically install the required extras just for unit tests (this also ensures that they are on the correct version in case someone has not updated in a while), runs the unittests, and then re-installs all extras. Optionally, it can also run the autoformat.sh script.