[code-infra] Migrate all the tests to vitest and remove mocha and karma remains

[michaldudak]

• Move regression/e2e tests from webpack to vite and use vitest to test (PR)
• test:coverage scripts
• Use vitest in browserstack tests
• Replace pnpm test:karma:profile
• Clean up actual tests (e.g. test skipping code)
• Remove deps related to mocha/karma
• Update test/README.md

[mj12albert]

This could be a viable way to set up Vitest + BrowserStack: https://chialab.github.io/rna/guide/vitest-provider-browserstack.html