chore: migrate to ESLint flat config

[eglitise]

This PR migrates from the ESLint legacy eslintrc format to the new flat config format. Some additional changes were also required here:

• The import module was removed as an explicit import, since it was not configured any further, and its rules are already being applied as part of @appium/eslint-config-appium-ts
• The react-native module was removed, as does not seem to be actively maintained and is unlikely to be updated for ESLint 9 compatibility (and also this codebase does not use React Native anyway)
• The configuration for the no-unused-vars rule was removed and instead applied to the @typescript-eslint/no-unused-vars rule (from @appium/eslint-config-appium-ts), which extends no-unused-vars
• The configuration for the react/jsx-uses-vars rule was removed, since the @typescript-eslint/no-unused-vars rule seems to detect JSX variables just fine
• Since .eslintignore is now integrated into the config file, the ignored file patterns have been changed to extend the .gitignore file

[mykola-mokhnach]

It would be interesting to know if we could do the same for other appium modules. Last time I checked it the typescript stuff was still not compatible with eslint 9

[eglitise]

I think we can likely migrate to flat config everywhere, but probably not to ESLint 9.
Flat config can still parse config information in legacy format (like @appium/eslint-config-appium-ts in this case), but ESLint 9 requires plugins to support it. The Typescript plugins do have support for ESLint 9 since version 8, but some others do not. It might also be worth switching from eslint-plugin-import to eslint-plugin-import-x, which has several improvements.