OpenTelemetry-Go: Log gRPC exporter ignores env TLS certs, bypassing mTLS/pinning

Summary The OTLP log gRPC exporter loads TLS settings from environment variables but does not apply them when creating gRPC transport credentials. Operators who rely on OTELEXPORTEROTLPLOGSCERTIFICATE, OTELEXPORTEROTLPCERTIFICATE, or related client certificate variables for CA pinning or mTLS get...