chore/update metrics

[poshinchen]

Description

Start emitting metrics in Strands to the collector if configured.

Documentation PR

Will add them once the exporter work is finished

Type of Change

Other (please describe):

Emit strands metrics

Testing

• I ran hatch run prepare
• Unit tests
• Manually setup meter and view metrics in console:

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

# Set up metrics with console exporter

from opentelemetry import metrics
from opentelemetry.sdk.resources import Resource
from opentelemetry.sdk.metrics import MeterProvider
from opentelemetry.sdk.metrics.export import ConsoleMetricExporter, PeriodicExportingMetricReader

console_metric_reader = PeriodicExportingMetricReader(ConsoleMetricExporter())
metrics_provider = MeterProvider(resource=resource, metric_readers=[console_metric_reader])
metrics.set_meter_provider(metrics_provider)

agent = Agent(tools=[calculator])
result = agent("what is 16*16?")

## Checklist
- [x] I have read the CONTRIBUTING document
- [x] I have added any necessary 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, or no new docs are needed
- [x] My changes generate no new warnings
- [ ] Any dependent changes have been merged and published

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