maps_react: fix indetermined execution order causing the polygon

[goapunk]

callback to be executed before the map object is created. Instead of relying on the refs, use the useMap hook and conditional rendering for the polygon.

Not sure if this is the best approach but for now it makes the maps work again on design-dev

fixes https://github.com/liqd/a4-meinberlin/issues/5582

to reproduce the error add the following to your webpack.dev.js:

module.exports = merge(common, {
    devtool: 'eval-source-map',
    optimization: {
       'nodeEnv': 'production'
     }                                    
})                                                                          

and try to create a mapidea or proposal

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