v2.12.0

What's Changed

feat(otel): consolidate all metrics on OpenTelemetry (#57)

Remove legacy Prometheus metrics from grpc/ and temporal/ packages, consolidating all metrics on OpenTelemetry.

grpc/: Delete MetricsManager, remove enableMetrics/metricsPath/enableLogging config options, add OTel observable gauges for server uptime/start_time.

temporal/: Replace tally/Prometheus with temporalotel.MetricsHandler. Simplify NewClient from (client.Client, io.Closer, error) to (client.Client, error). Fixes Go 1.22+ panic from duplicate http.Handle("/metrics").

Dependencies removed: uber-go/tally/v4, go.temporal.io/sdk/contrib/tally
Dependencies demoted: prometheus/client_golang (direct → indirect)

Breaking Changes

• grpc: WithMetrics(), WithoutMetrics(), WithMetricsPath(), WithLogging(), WithoutLogging(), GetMetricsManager() removed. Use WithOTelConfig() for metrics.
• temporal: NewClientWithMetrics() and MetricsListenAddress removed. NewClient signature changed to (client.Client, error).