feat(telemetry): forward provider_kwargs to MeterProvider in setup_meter

[aribault]

Motivation

StrandsTelemetry.setup_meter constructs an OpenTelemetry MeterProvider but only forwards resource and metric_readers. Users who need to pass other supported MeterProvider kwargs, most notably views, currently have to bypass setup_meter entirely and reconstruct the provider from scratch, as illustrated in the workaround the issue reporter shared.

This change accepts arbitrary keyword arguments and forwards them to MeterProvider, exposing the full surface without changing any existing behavior.

Resolves: #843

Public API Changes

setup_meter now accepts **provider_kwargs that are forwarded to MeterProvider. resource and metric_readers continue to be managed by the helper.

# Before — had to bypass setup_meter to attach views
meter_provider = MeterProvider(
    resource=resource,
    metric_readers=metrics_readers,
    views=[View(instrument_name="strands.tool.*", attribute_keys={"tool_name"})],
)
strands_telemetry.meter_provider = meter_provider
metrics_api.set_meter_provider(meter_provider)

# After
strands_telemetry.setup_meter(
    enable_otlp_exporter=True,
    views=[View(instrument_name="strands.tool.*", attribute_keys={"tool_name"})],
)

Existing callers are unaffected.