feat(csharp/src): Add support for adding and configuring OTel exporters

[birschick-bq]

Adds a new project and tests to support adding OpenTelemetry exporters (TracerProvider).

• Adds an ADBC FileExporter implementation.
• Adds a ExportersBuilder that
  • Builds a list of supported exporters
  • Activates and returns the appropriate exporter based on the passed option or environment variable setting.

Note to reviewer:
ExportersBuilder is a convenience class - let me know if you think it is useful.

[birschick-bq]

@CurtHagenlocher - Just a reminder to see if you can review this separate PR to handle exporting trace activity.