feat(e2e): add OTLP metrics export support to V2 E2E tests

[kpango]

This PR adds support for exporting E2E metrics (total requests, errors, latency, queue wait) to an OpenTelemetry Collector via OTLP.

Changes:

• Added Observability configuration to tests/v2/e2e/config/config.go.
• Implemented tests/v2/e2e/metrics/otel.go to adapt E2E metrics to OpenTelemetry Observable Gauges.
• Updated TestE2EStrategy in tests/v2/e2e/crud/strategy_test.go to initialize and register observability if enabled.

Metrics exported:

• e2e_total_requests (Int64)
• e2e_total_errors (Int64)
• e2e_latency_{p50,p90,p99,max,min} (Float64, ms)
• e2e_queue_wait_{p50,p90,p99,max} (Float64, ms)

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PR created automatically by Jules for task 3128213106735653582 started by @kpango

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