feat(search): geohash support in bleve

[dschmidt]

Description

bleve maps a <name>_geohash field next to the geopoint sibling of every geopoint field and writes the geohash from the batch, analyzed into one depth-tagged term per precision. That is the index a geohash grid for bleve can be built on (#3272), OpenSearch has geohash_grid natively. Nothing queries it yet. bleve only, the shared document shape is untouched. Additive on v5, no reindex.

Related Issue

• feat(search): geohash aggregation #3272
  This PR is a prerequisite for that one

How Has This Been Tested

• Encoder against the reference vector and as a prefix code
• Geohash written next to the geopoint sibling of every geopoint override, nested too, none without lat/lon
• Terms by precision through the batch: one document, one cell at precision 5

Types of changes

• New feature (non-breaking change which adds functionality)

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 471 complexity

Metric	Results
Complexity	471

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