Replace the old e2e tests with the Cypress integration tests

[obulat]

Description

This PR removes the old Selenium e2e tests that were too brittle/ redundant. Instead, we created the integration tests that test the workflow of several components together, using Cypress.

Technical details

The Cypress tests are moved to the tests directory instead of a separate 'cypress' directory.
The integration tests are added to the GitHub actions' 'Lint and Test' workflow CI.
Some documentation was updated accordingly.

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  visible errors.

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[zackkrida]

This is a big improvement for several reasons:

• No longer requires Java as a dependency
• Removes ~20k lines of code for the same test coverage
• The cypress helper functions streamline things nicely

Thank you!

[Cronus1007]

@obulat Shall I also extend the Cypress tests to the new functionality that has been added recently to the repository.
Plus there is a need to extend the Cypress tests for checking the functionality of helper section.