Use class instance of axios in REST helper

[vanvoljg]

Motivation/Description of the PR

• Use class instance of axios, not the global instance, to avoid contaminating global configuration.
• Fixes REST helper: Global axios instance gets mutated #2652

I'm not sure I can think of any new tests for this, the REST helper seems quite well tested already....

Applicable helpers:

• WebDriver
• Puppeteer
• Nightmare
• REST
• FileHelper
• Appium
• Protractor
• TestCafe
• Playwright

Applicable plugins:

• allure
• autoDelay
• autoLogin
• customLocator
• pauseOnFail
• puppeteerCoverage
• retryFailedStep
• screenshotOnFail
• selenoid
• stepByStepReport
• wdio

Type of change

• 🔥 Breaking changes
• 🚀 New functionality
• 🐛 Bug fix
• 📋 Documentation changes/updates
• ♨️ Hot fix
• 🔨 Markdown files fix - not related to source code
• 💅 Polish code

Checklist:

• Tests have been added
• Documentation has been added (Run npm run docs)
• Lint checking (Run npm run lint)
• Local tests are passed (Run npm test)

[DavertMik]

Thanks, this is a good change