Added index tests and fixed /index/_dangling.

[dblock]

Description

Added index tests. All except stats which needs schema work.

Fixed /{index}/_dangling that can return nodes and cluster_name.

Upgraded tests to use OpenSearch 2.15 because /{index}/_forcemerge with primary_only was added in OpenSearch 2.13.

Found a bug in the documentation doing this, opensearch-project/documentation-website#7657.

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[github-actions]

Changes Analysis

Commit SHA: 71256f3
Comparing To SHA: ba3d715

API Changes

Summary

└─┬Paths
  └─┬/_dangling
    └─┬GET
      └─┬Responses
        └─┬200
          └─┬application/json
            └─┬Schema
              ├──[➕] properties (23659:15)
              └──[➕] properties (23661:15)

Document Element	Total Changes	Breaking Changes
paths	2	0

• Total Changes: 2
• Additions: 2

Report

The full API changes report is available at: https://github.com/opensearch-project/opensearch-api-specification/actions/runs/9861391199/artifacts/1683174817

API Coverage

	Before	After	Δ
Covered (%)	483 (47.31 %)	483 (47.31 %)	0 (0 %)
Uncovered (%)	538 (52.69 %)	538 (52.69 %)	0 (0 %)
Unknown	24	24	0