OTEL_BLRP_EXPORT_TIMEOUT should do something

[DylanRussell]

Currently it doesn't do anything. This was uncovered in #4535.

Need to figure out how it should behave when the OTLP exporter(s) already had it's export timeout flag set via another env var.

[lzchen]

@DylanRussell

Does this apply to the other batch span/metric processors too?

[DylanRussell]

Yeah good question, same exact issue for the Batch span processor.

I'm pretty sure also an issue on the metric processor, it gets passed through to collect, and I'm not sure where collect is implemented.. But the metric exporter doesn't do anything with it's timeout param, so even if it's getting passed through to that it's not being used there.