feat: add meter

[poshinchen]

Description

Initiated OTEL Meter in Strands in order to send metrics.

Note:
User has to setup global meter_provider for strands to use them directly (will update the documentation).

Documentation PR

Will update the documentation along with the traces.

Type of Change

• New feature

Testing

• Added unit tests

• hatch fmt --linter
• hatch fmt --formatter
• hatch test --all

• Tested manually with and without global OTEL Meter setup:

# Set up the resource
resource = Resource.create({ResourceAttributes.SERVICE_NAME: "strands-otel-test", "environment": "test"})

# Set up metrics with console exporter
console_metric_reader = PeriodicExportingMetricReader(ConsoleMetricExporter())
metrics_provider = MeterProvider(resource=resource, metric_readers=[console_metric_reader])
metrics.set_meter_provider(metrics_provider)

• Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

Checklist

• I have read the CONTRIBUTING document
• I have added tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature
• My changes generate no new warnings
• Any dependent changes have been merged and published

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