[exporter/elasticsearch] Merge *.geo.location.{lat,lon} to *.geo.location in OTel mode (open-telemetry#36594)

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Ex. Adding a feature - Explain what this achieves.-->
#### Description

In OTel mapping mode, merge *.geo.location.{lat,lon} to *.geo.location
such that they are stored as
[geo_point](https://www.elastic.co/guide/en/elasticsearch/reference/current/geo-point.html)
in Elasticsearch.

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes open-telemetry#36565

<!--Describe what testing was performed and which tests were added.-->
#### Testing

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#### Documentation

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---------

Co-authored-by: Vishal Raj <[email protected]>

Author: 2 people

exporter/elasticsearchexporter/model_test.go

@@ -1329,3 +1329,36 @@ func TestEncodeLogBodyMapMode(t *testing.T) {
 	require.Error(t, err)
 	require.ErrorIs(t, err, ErrInvalidTypeForBodyMapMode)
 }
+
+func TestMergeGeolocation(t *testing.T) {
+	attributes := map[string]any{
+		"geo.location.lon":          1.1,
+		"geo.location.lat":          2.2,
+		"foo.bar.geo.location.lon":  3.3,
+		"foo.bar.geo.location.lat":  4.4,
+		"a.geo.location.lon":        5.5,
+		"b.geo.location.lat":        6.6,
+		"unrelatedgeo.location.lon": 7.7,
+		"unrelatedgeo.location.lat": 8.8,
+		"d":                         9.9,
+		"e.geo.location.lon":        "foo",
+		"e.geo.location.lat":        "bar",
+	}
+	wantAttributes := map[string]any{
+		"geo.location":              []any{1.1, 2.2},
+		"foo.bar.geo.location":      []any{3.3, 4.4},
+		"a.geo.location.lon":        5.5,
+		"b.geo.location.lat":        6.6,
+		"unrelatedgeo.location.lon": 7.7,
+		"unrelatedgeo.location.lat": 8.8,
+		"d":                         9.9,
+		"e.geo.location.lon":        "foo",
+		"e.geo.location.lat":        "bar",
+	}
+	input := pcommon.NewMap()
+	err := input.FromRaw(attributes)
+	require.NoError(t, err)
+	mergeGeolocation(input)
+	after := input.AsRaw()
+	assert.Equal(t, wantAttributes, after)
+}