Update to React 18

[AlekseyManetov]

1. Update 'react-focus-lock' when the issue is resolved [React 18.0.0] Must explicitly specify the prop children for class and functional components theKashey/react-focus-lock#215
2. Update 'react-markdown'
3. Update 'react-custom-scrollbars-2' when the issue is resolved Can not install with react 18 RobPethick/react-custom-scrollbars-2#27
4. Replace 'react-measure' last updated 2 years ago
5. Update 'react-router'

[AlekseyManetov]

please pay attention on portal users(like Dropdown and Tooltip) that they don't create extra portal nodes on open

[vasilii-kovalev]

please pay attention on portal users(like Dropdown and Tooltip) that the don't create extra portal nodes on open

I've faced the problems with Dropdown component and created a little demo to illustrate them (and test, when the library is updated): https://codesandbox.io/s/uui-dropdown-react-18-issue-mjhlrh

There are 2 issues in there:

1. When hovering over the dropdown button (expected trigger is hover), the hidden text appears in the top left corner first, then, after a short time, appears when it belongs
2. When clicking on the button (which shows the content on hover), an error occurs:
   

Hope it will be useful.

[blackymax]

I've faced with problem when using Tooltip, looks to needs rework of tooltip body render in according to usage with React 18