[Generation] Create configuration model generation action and dialog window

We should be able to see action in the NEW context menu between other context actions provided by plugin.
It should appear only by clicking on the module system.xml file.
Also, should be checked if it is possible to add markers to the fields in the system.xml file to generated a single field value accessor.

Also, corresponding dialog window should be provided. It should ask next info from the user:

1. path to target dir from the root
2. configuration model name
3. flag if fields should be updated if they already exist
4. which fields should be generated (they should be retrieved by the corresponding parser https://github.com/magento/magento2-phpstorm-plugin/issues/1164)
5. would be great to add a generation result preview

**Additional context**

**Mainline branch:** mainline/generate-configuration-model