feat: Setup metric provider for manual and auto-instrumented measurements

[morgan-wowk]

TL;DR

Added OpenTelemetry metrics support with configurable aggregation temporality alongside existing tracing functionality.

What changed?

• Added metrics.py module to configure OpenTelemetry meter provider with OTLP exporters (gRPC and HTTP)
• Extended configuration system to support metrics exporter endpoints via TANGLE_OTEL_METRIC_EXPORTER_ENDPOINT and TANGLE_OTEL_METRIC_EXPORTER_PROTOCOL environment variables
• Implemented configurable aggregation temporality for different metric instrument types (counter, histogram, etc.) through environment variables like TANGLE_OTEL_METRICS_TEMPORALITY_COUNTER
• Added temporality.py module to map string-based temporality configuration to OpenTelemetry SDK types
• Updated providers.setup() to initialize both tracing and metrics providers when configured
• Exported setup_metrics function in the package's public API

How to test?

Set the TANGLE_OTEL_METRIC_EXPORTER_ENDPOINT environment variable to your OTLP collector endpoint and call providers.setup(). Optionally configure temporality settings using the TANGLE_OTEL_METRICS_TEMPORALITY_* environment variables. The system will work with metrics-only, tracing-only, or both configurations.

Why make this change?

This enables comprehensive observability by adding metrics collection capabilities to complement the existing distributed tracing functionality, allowing applications to export both traces and metrics to OpenTelemetry collectors with fine-grained control over aggregation behavior.

[morgan-wowk]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat: Measure system errors using a counter #127
• feat: Setup metric provider for manual and auto-instrumented measurements #126 👈 (View in Graphite)
• chore!: Refactor OTel exporters to be signal-specific #125
• feat: Set service version on OTel data #124
• chore: Refactor OTel concerns in preparation for metric provider #123
• master

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