Create BatchSpanProcessor from env in TracerProvider (#445)

This allows for configuring BSP when just `with_exporter` is used, instead of requiring users to create the BSP themselves when they want to pull from the environment.

Author: samschlegel

opentelemetry/src/sdk/trace/provider.rs

@@ -116,11 +116,11 @@ impl Builder {
         // drop. We cannot assume we are in a multi-threaded tokio runtime here, so use
         // `spawn_blocking` to avoid blocking the main thread.
         let spawn = |fut| tokio::task::spawn_blocking(|| futures::executor::block_on(fut));
-        let batch = sdk::trace::BatchSpanProcessor::builder(
+        let batch = sdk::trace::BatchSpanProcessor::from_env(
             exporter,
             spawn,
-            tokio::time::sleep,
             crate::util::tokio_interval_stream,
+            tokio::time::sleep,
         );
         self.with_batch_exporter(batch.build())
     }
@@ -129,11 +129,11 @@ impl Builder {
     #[cfg(all(feature = "async-std", not(feature = "tokio")))]
     #[cfg_attr(docsrs, doc(cfg(feature = "async-std")))]
     pub fn with_exporter<T: SpanExporter + 'static>(self, exporter: T) -> Self {
-        let batch = sdk::trace::BatchSpanProcessor::builder(
+        let batch = sdk::trace::BatchSpanProcessor::from_env(
             exporter,
             async_std::task::spawn,
-            async_std::task::sleep,
             async_std::stream::interval,
+            async_std::task::sleep,
         );
         self.with_batch_exporter(batch.build())
     }