feat(o11y): self-logs via shared entry-point zap->OTel bridge + OTLP log export (PIPE-1066) - #287

Proposed Change

Bridges blitz's own zap logging into an OTel LoggerProvider so internal logs export as
OTLP records, opt-in through telemetry.logs. The logger is bridged once at each process
entry point (main for standalone; config.LoadModules and the embed runner for embed),
and shared from there. A bridged zap logger propagates to the child loggers components
derive, so components do not re-bridge. Also collapses the host's flat provider fields
into the single Host.Telemetry bundle, so one value carries all three signals.

Each setting is exposed on all three config surfaces, like every other blitz option: the
telemetry.logs config block, BLITZ_TELEMETRY_LOGS_* env vars, and --telemetry-logs-*
flags.

How to validate

• Point blitz at any OTLP gRPC collector (its debug exporter shows the log records). Run:
  go run ./cmd/blitz --generator-type apache-common --generator-apache-common-rate 1s --output-type stdout --telemetry-logs-otlpendpoint localhost:4317 --telemetry-logs-insecure
• Confirm blitz's own startup and generator log lines arrive at the collector as OTLP
  records. They still print to stdout too.
• Drop the two --telemetry-logs-* flags and confirm logging stays stdout-only.
• go test ./embed/ runs TestEmbed_HostBundleReceivesAllThreeSelfSignals, which asserts
  one host bundle receives metrics, spans, and bridged logs together.
• go test ./internal/config/... covers the flag, env, and default for each new setting.

Checklist

• Changes are tested
• CI has passed