Migrate the code for nearest tree to query API new spec.

Prerequisite: https://github.com/Greenstand/treetracker-query-api/issues/78

Currently the `nearest tree` feature (the arrow icon indicating the nearest tree on the map when people get lost on the map) is using the old API, now we need to switch to the new API.

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Some hints:

- Please read our [readme](https://github.com/Greenstand/treetracker-web-map-core#treetracker-web-map-core) for more information/guide/tutorial.
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Start with the repository README and prerequisite issue #78, then locate the nearest-tree map feature and its current API call. Update that feature to use the new query API specification; done means the map's nearest-tree arrow works through the new API. No file or test is named in the issue.

Written by the indexing model from the issue text.