3.31.0

• Fixed execute_with_retries returning a large result set split across several ResultSet objects: row-format stream parts that share a result_set_index are now concatenated back into a single result set, so a large SELECT is returned as one result set instead of one per stream chunk
• Introduce ydb.observability — vendor-neutral tracing entrypoint with a TracingProvider interface; enable_tracing(provider) accepts any implementation (custom or OpenTelemetry) and replaces the previously installed one. The SDK core no longer imports opentelemetry, so tracing can be enabled without the OpenTelemetry packages by supplying a custom provider
• When tracing is enabled the SDK appends a ydb-sdk-tracing/0.1.0 token to the x-ydb-sdk-build-info header, so the server can distinguish requests from tracing-enabled clients
• Add client-side metrics through the same vendor-neutral ydb.observability layer: enable_metrics(provider) / disable_metrics(), with ydb.opentelemetry.enable_metrics(meter_provider=None) as the OpenTelemetry convenience. Instruments cover client operation duration/failures, retry duration/attempts, and query session pool state. QuerySessionPool gains an optional name argument for the pool metric label. When metrics are enabled the SDK appends a ydb-sdk-metrics/0.1.0 token to the x-ydb-sdk-build-info header

Full Changelog: 3.30.0...3.31.0