feat: add multi clusters support

[ValeraS]

Usage

<script>
window.web_version=true
window.custom_backend='';
window.meta_backend='/api/meta';
</script>

import {StaffCard} from 'staff-card-library';
import {
    MultiClusterApp as App,
    configureStore,
    ErrorBoundary,
    componentsRegistry,
    settingsManager,
    setUserSettings,
} from 'ydb-embedded-ui';

import {AsideNavigation} from '../containers/AsideNavigation/AsideNavigation';
import {userSettings} from '../containers/AsideNavigation/settings';

const {store, history} = configureStore();

const settings = settingsManager.extractSettingsFromLS(DEFAULT_INTERNAL_USER_SETTINGS);
store.dispatch(setUserSettings(settings));

componentsRegistry.set('StaffCard', StaffCard).set('AsideNavigation', AsideNavigation);

function render() {
    ReactDOM.render(
        <ErrorBoundary>
            <App store={store} history={history} userSettings={userSettings} />
        </ErrorBoundary>,
        document.getElementById('root'),
    );
}

render();

[artemmufazalov]

Since there are a lot of changes here, it should be released with breaking changes as v5.0.0

[artemmufazalov]

Discussed with team lead, there are some users, that deploy ydb with several clusters and want to use multi cluster UI version.

If it's possible, it would be perfect to have separate commands for embedded version and multi-cluster version (I shortened it to mcv):

"dev:embedded": "REACT_APP_BACKEND=http://localhost:8765 npm start",
"dev:mcv": "META_YDB_BACKEND=meta_host_placeholder npm start",
"build:embedded": "...",
"build:mcv": "...",

Or at least there should be a section with MCV description in README or wiki - how to run in dev mode, how to build, etc.

[artemmufazalov]

Discussed with team lead, there are some users, that deploy ydb with several clusters and want to use multi cluster UI version.
Or at least there should be a section with MCV description in README or wiki - how to run in dev mode, how to build, etc.

Update: mvp (meta backend) repo won't be public, without backend code this feature is not publicly needed. So separate multi-cluster version commands are not needed. Wiki page will be helpful, though