Added db metric reporting and config options.

[Randy808]

No description provided.

[Copilot]

Pull Request Overview

This PR adds database metric reporting capabilities and configuration options for RocksDB performance tuning. The changes enable monitoring of RocksDB internals through Prometheus metrics and provide configurable parameters for memory usage and parallelism.

• Added comprehensive RocksDB metrics collection for memory tables, compactions, and cache usage
• Introduced configuration options for block cache size, parallelism, and write buffer size
• Integrated metrics exporter with background thread to periodically update gauges

Reviewed Changes

Copilot reviewed 6 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/new_index/db_metrics.rs	New module defining RocksDB metrics structure with comprehensive gauge collections
src/new_index/db.rs	Enhanced DB struct with metrics export functionality and configurable RocksDB options
src/new_index/schema.rs	Updated Store constructor to accept metrics and initialize DB stats exporters
src/new_index/mod.rs	Added db_metrics module export
src/config.rs	Added command-line arguments and config fields for RocksDB tuning parameters
tests/common.rs	Updated test configuration with new DB parameter defaults

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[Randy808]

I amended the commit with copilot's suggestions

[RCasatta]

utACK 027e38d