feat(search): geohash support in bleve

[dschmidt]

Description

with this PR 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 25 complexity

Metric	Results
Complexity	25

View in Codacy

🟢 Coverage 93.15% diff coverage · +0.04% coverage variation

Metric	Results
Coverage variation	✅ +0.04% coverage variation (-1.00%)
Diff coverage	✅ 93.15% diff coverage

View coverage diff in Codacy

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (8f27a91)	92568	23164	25.02%
Head commit (58c52b7)	92640 (+72)	23217 (+53)	25.06% (+0.04%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#3519)	73	68	93.15%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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