Query Input Assistance: validate spelling mistakes in field names

## Description

With https://github.com/Graylog2/graylog2-server/issues/11503 we are now validating spelling mistakes in field values, while writing a search query. The next step is validating spelling mistakes in field names. While the validation of field values happens in the backend, we should validate spelling mistakes in field names in the frontend, since we already have access to all available field names.

The validation of spelling mistakes in field values is based on the levenshtein distance, we should implement the same logic for the validation of field names.