An implementation of the OpenTelemetry SDK for Perl

Changes for 0.019 - 2023-11-23T19:31:08+00:00

• Validate span processors when adding them to the TracerProvider
• Shutting down a TracerProvider that has been shutdown is not en error and no longer warns
• Add documentation for TracerProvider's add_span_processor
• Make all shutdown and force_flush methods async for consistency
• Remove lock from span to avoid running into file descriptor limits (GH #8)