[exporter] [chore] move exporter.exporterhelper.request to internal (#11042)

#### Description

This PR moves `exporter/exporterhelper/request.go` to
`exporter/internal/request.go` to avoid circular dependency.

Context: As part of the effort to move from a queue->batch pushing model
to a queue->batch pulling model in exporter, we will be depending on
`Request` from `exporter/exporterbatcher`. However,
`exporter/exporterhelper` already depends on `exporter/exporterbatcher`,
so we need to move `Request` out of `exporter/exporterhelper`

#### Link to tracking issue

https://github.com/open-telemetry/opentelemetry-collector/issues/10368

#### Testing

Ran `opentelemetry-collector$ make` to make sure all tests still pass.

exporter/exporterhelper/exporterhelper.go

@@ -0,0 +1,24 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exporterhelper // import "go.opentelemetry.io/collector/exporter/exporterhelper"
+import "go.opentelemetry.io/collector/exporter/internal"
+
+// Request represents a single request that can be sent to an external endpoint.
+// Experimental: This API is at the early stage of development and may change without backward compatibility
+// until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
+type Request = internal.Request
+
+// RequestErrorHandler is an optional interface that can be implemented by Request to provide a way handle partial
+// temporary failures. For example, if some items failed to process and can be retried, this interface allows to
+// return a new Request that contains the items left to be sent. Otherwise, the original Request should be returned.
+// If not implemented, the original Request will be returned assuming the error is applied to the whole Request.
+// Experimental: This API is at the early stage of development and may change without backward compatibility
+// until https://github.com/open-telemetry/opentelemetry-collector/issues/8122 is resolved.
+type RequestErrorHandler = internal.RequestErrorHandler
+
+// extractPartialRequest returns a new Request that may contain the items left to be sent
+// if only some items failed to process and can be retried. Otherwise, it returns the original Request.
+func extractPartialRequest(req Request, err error) Request {
+	return internal.ExtractPartialRequest(req, err)
+}

exporter/internal/request.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exporterhelper // import "go.opentelemetry.io/collector/exporter/exporterhelper"
+package internal // import "go.opentelemetry.io/collector/exporter/internal"
 
 import (
 	"context"
@@ -34,7 +34,7 @@ type RequestErrorHandler interface {
 
 // extractPartialRequest returns a new Request that may contain the items left to be sent
 // if only some items failed to process and can be retried. Otherwise, it returns the original Request.
-func extractPartialRequest(req Request, err error) Request {
+func ExtractPartialRequest(req Request, err error) Request {
 	if errReq, ok := req.(RequestErrorHandler); ok {
 		return errReq.OnError(err)
 	}