RCBC-526: Add support for meters

[DemetrisChr]

Motivation

As part of the observability work, we need to add support for collecting metrics, following the Extended Observability RFC.

Changes

• Add Meter and ValueRecorder abstract base classes
• Extend the observability wrapper to report metrics for every operation, at the same level as the top-level operation span.
• Add Ruby bindings for the HDR Histogram implementation used by the C++ core.
• Add a default LoggingMeter implementation. This utilizes the HDR Histogram Ruby bindings.
• Disable metrics in the C++ core, as metric collection now happens entirely on the Ruby side.

[Copilot]

Pull request overview

This PR adds support for metrics collection in the Couchbase Ruby SDK. The implementation introduces a meter abstraction with logging and noop implementations, along with test utilities for metrics verification.

Key changes:

• Added metrics infrastructure with Meter and ValueRecorder interfaces
• Integrated metrics collection into the observability layer to track operation durations
• Added HDR histogram implementation for efficient percentile calculations

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
lib/couchbase/metrics/*.rb	Core metrics interfaces (Meter, ValueRecorder) and implementations (NoopMeter, LoggingMeter)
lib/couchbase/utils/observability.rb	Integrated metrics collection into operation tracking with error handling
lib/couchbase/options.rb	Added meter configuration option to Cluster options
lib/couchbase/cluster.rb	Wired up meter initialization with LoggingMeter as default
lib/couchbase/utils/hdr_histogram.rb	Ruby wrapper for HDR histogram percentile calculations
ext/rcb_hdr_histogram.*	C++ extension for HDR histogram functionality
test/utils/metrics/*.rb	Test utilities for metrics verification
test/*_test.rb	Integration tests for metrics collection
ext/rcb_backend.cxx	Disabled core-level metrics in favor of wrapper-side handling

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[Copilot]

Pull request overview

Copilot reviewed 26 out of 26 changed files in this pull request and generated 1 comment.

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