Add user journey test for canceling a build

[peytondmurray]

Fixes #674.

Description

This PR adds a user journey test for canceling a build.

This pull request:

• Adds a new user journey test
• Refactors some of api_utils.py to use a new wait_for_condition function to poll the conda-store-server

Pull request checklist

• [x] Did you test this change locally?
• [x] Did you update the documentation (if required)?
• [x] Did you add/update relevant tests for this change (if required)?

How to test

Run the conda-store server:

docker compose up

Then run the test:

cd conda-store-server
pytest tests/user_journeys/test_user_journeys.py::test_cancel_build

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