Merge otel into one file and add package doc (#1176)

No need to split a tiny package into multiple files. Also adding package doc for the otel package.

doc.go

@@ -12,4 +12,5 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package otel contains OpenTelemetry Go packages.
 package otel // import "go.opentelemetry.io/otel"

otel.go

@@ -25,3 +25,10 @@ type Tracer = trace.Tracer
 type Meter = metric.Meter
 
 type Propagators = propagation.Propagators
+
+// ErrorHandler handles irremediable events.
+type ErrorHandler interface {
+	// Handle handles any error deemed irremediable by an OpenTelemetry
+	// component.
+	Handle(error)
+}