Working on #76082 I found that src/test_utils is outdated and has a dependency on data plugin. We need to clean up the project and remove the dependency on plugins.

• https://github.com/elastic/kibana/blob/master/src/test_utils/get_url.js used in 2 functional tests, might be moved to a @kbn/test

Move to data plugin (fix #78518)

• https://github.com/elastic/kibana/blob/master/src/test_utils/public/stub_index_pattern.js

Not used (removed in #76528)

• https://github.com/elastic/kibana/blob/master/src/test_utils/public/static_html_id_generator.js
• https://github.com/elastic/kibana/blob/master/src/test_utils/expect_deep_equal.js
• https://github.com/elastic/kibana/blob/master/src/test_utils/public/simulate_keys.js
• https://github.com/elastic/kibana/blob/master/src/test_utils/public/ng_mock.js
• https://github.com/elastic/kibana/blob/master/src/test_utils/public/image_comparator.js
• https://github.com/elastic/kibana/blob/master/src/test_utils/public/mocks/intl.js

All the remaining code should be converted into TypeScript.