### Description

It would be really great if [CircleProcessor.java](https://github.com/elastic/elasticsearch/blob/0699c9351f1439e246d408fd6538deafde4087b6/x-pack/plugin/spatial/src/main/java/org/elasticsearch/xpack/spatial/ingest/CircleProcessor.java) could be published in some maven artifact.
We are thinking to convert Geoshape Circle into Geoshape Polygon on application side instead of ElasticSearch Server side. The benefits of it is that it would make possible for us to choose `error_distance` dynamically depending on different conditions.
With direct code access to [CircleProcessor.java](https://github.com/elastic/elasticsearch/blob/0699c9351f1439e246d408fd6538deafde4087b6/x-pack/plugin/spatial/src/main/java/org/elasticsearch/xpack/spatial/ingest/CircleProcessor.java) and [SpatialUtils.java](https://github.com/elastic/elasticsearch/blob/0699c9351f1439e246d408fd6538deafde4087b6/x-pack/plugin/spatial/src/main/java/org/elasticsearch/xpack/spatial/SpatialUtils.java) it would be possible to make application side custom conversion logic.
ElasticSearch version: >= 8
x-pack/plugin/spatial/src/test/java/org/elasticsearch/xpack/spatial/ingest/CircleProcessorTests.java
assertThat(e.getMessage(), equalTo("invalid circle definition"));
    }
    public void testMissingField() {
        IngestDocument ingestDocument = TestIngestDocument.emptyIngestDocument();
        CircleProcessor processor = new CircleProcessor("tag", null, "field", "field", false, 10, GEO_SHAPE);
        IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> processor.execute(ingestDocument));
        assertThat(e.getMessage(), equalTo("field [field] not present as part of path [field]"));
    }
    public void testInvalidType() {
        Map<String, Object> field = new HashMap<>();
        field.put("coordinates", List.of(100, 100));
        field.put("radius", "10m");
        Map<String, Object> map = new HashMap<>();
        map.put("field", field);
        IngestDocument ingestDocument = TestIngestDocument.withDefaultVersion(map);
        CircleProcessor processor = new CircleProcessor("tag", null, "field", "field", false, 10, GEO_SHAPE);
        for (Object value : new Object[] { null, 4.0, "not_circle" }) {
            field.put("type", value);
            IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> processor.execute(ingestDocument));
            assertThat(e.getMessage(), equalTo("invalid circle definition"));
        }
    }
    public void testInvalidCoordinates() {
        Map<String, Object> field = new HashMap<>();
        field.put("type", "circle");
        field.put("radius", "10m");
        Map<String, Object> map = new HashMap<>();
        map.put("field", field);
        IngestDocument ingestDocument = TestIngestDocument.withDefaultVersion(map);
        CircleProcessor processor = new CircleProcessor("tag", null, "field", "field", false, 10, GEO_SHAPE);