Distinguishing different types of tests #263

As a Code PushUp contributor, I want to be able to add and view test files and be able to tell at the first glance what their scope is.

This issue is a part of #145

Implementation details

• Each type of test has a separate nx target and runs in a separate CI pipeline job for every major OS.
• Add an ESLint rule to enforce the new naming.
• Each type of test has a separate vite config.
• Rename tsconfig.spec to tsconfig.test and include all test patterns in it.
• Adjust coverage pipeline for unit and integration tests.

E2E tests

• Test the full flow in a real environment.
• nx target test-e2e
• Live in a separate e2e folder.
• E2E test files have the .e2e.test.ts suffix.

Integration tests

• Test a bigger unit (e.g. a plugin) or an integration with a 3rd party tooling (e.g. multi-progress-bars).
• nx target test-integration
• Live next to their implementation files.
• Have the .integration.test.ts suffix.

Unit tests

• Test a small unit (a function) which can be run in an isolated environment.
• nx target test-unit
• Live next to their implementation files.
• Have the .unit.test.ts suffix.