[AFR Ask] Send the reason when making getDeltas calls (#22821)

Fixes:
[AB#6959](https://dev.azure.com/fluidframework/235294da-091d-4c29-84fc-cdfc3d90890b/_workitems/edit/6959)

## Description
Yang Gao to detail the specifics and data/incident information in the
Feature Description

Optimize getDelta / internal service calls to reduce load on Alfred &
Riddler and minimize impact on customer traffic

FRS has observed some unexpected getDeltas calls. If the client can send
FRS the reasons why the calls were made, it can greatly help the
investigations. One example is that we have seen some getDeltas calls
trying to read very old ops, which were generated tens of days ago, and
it's hard for us to understand what triggered these calls.

## Reviewer Guidance

Let me know if there's a better way to send the reason to AFR.

packages/drivers/routerlicious-driver/src/deltaStorageService.ts

@@ -91,7 +91,13 @@ export class DocumentDeltaStorageService implements IDocumentDeltaStorageService
 				this.snapshotOps = undefined;
 			}
 
-			const ops = await this.deltaStorageService.get(this.tenantId, this.id, from, to);
+			const ops = await this.deltaStorageService.get(
+				this.tenantId,
+				this.id,
+				from,
+				to,
+				fetchReason,
+			);
 			validateMessages("storage", ops.messages, from, this.logger, false /* strict */);
 			opsFromStorage += ops.messages.length;
 			return ops;
@@ -144,6 +150,7 @@ export class DeltaStorageService implements IDeltaStorageService {
 		id: string,
 		from: number, // inclusive
 		to: number, // exclusive
+		fetchReason?: string,
 	): Promise<IDeltasFetchResult> {
 		const ops = await PerformanceEvent.timedExecAsync(
 			this.logger,
@@ -158,6 +165,7 @@ export class DeltaStorageService implements IDeltaStorageService {
 				const response = await restWrapper.get<ISequencedDocumentMessage[]>(url, {
 					from: from - 1,
 					to,
+					fetchReason: fetchReason ?? "",
 				});
 				event.end({
 					length: response.content.length,