Function helpers are static functions that are available in Eel without a containing helper. This
change removes the default q variable and instead adds a static method `q` to the flowQuery
class that can be used as helper function with the following configuration:

```
Neos:
  Fusion:
    defaultContext:
      q: 'Neos\Eel\FlowQuery\FlowQuery::q'
  ContentRepository:
    labelGenerator:
      eel:
        defaultContext:
          q: Neos\Eel\FlowQuery\FlowQuery::q
```

Co-Authored-By: Alexander Berl <a.berl@outlook.com>

Co-Authored-By: Karsten Dambekalns <karsten@dambekalns.de>