Cypress. Rework the command to add a label.

[dvkruchinin]

Motivation and context

When running tests without splitting into groups, as is done in Publish Docker images there will be an error in test canvas3d_functionality_2/case_78_canvas3d_functionality_cuboid_label.js. This is due to the fact that a new label is not added if a label with the same name already exists. This is also due to changes in #4007. This patch solves this problem.
Before adding a new label, it is checked that a label with the same name does not exist. Otherwise, the existing label will be deleted.
The command to delete the label has been added, the label addition command has been redesigned and some tests have been adapted.

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2022 Intel Corporation
#
# SPDX-License-Identifier: MIT