Make the diagnostic log downloader logs clearly say what they are.

Just saying "BDX" can make people think this is OTA.

Author: bzbarsky-apple

src/darwin/Framework/CHIP/MTRDiagnosticLogsDownloader.mm

@@ -476,7 +476,7 @@ - (void)handleBDXTransferSessionBeginForFileDesignator:(NSString *)fileDesignato
                                           abortHandler:(AbortHandler)abortHandler;
 {
     assertChipStackLockedByCurrentThread();
-    MTR_LOG("BDX Transfer Session Begin: %@", fileDesignator);
+    MTR_LOG("BDX Transfer Session Begin for log download: %@", fileDesignator);
 
     auto * download = [_downloads get:fileDesignator fabricIndex:fabricIndex nodeID:nodeID];
     VerifyOrReturn(nil != download, completion([MTRError errorForCHIPErrorCode:CHIP_ERROR_NOT_FOUND]));
@@ -492,7 +492,7 @@ - (void)handleBDXTransferSessionDataForFileDesignator:(NSString *)fileDesignator
                                            completion:(MTRStatusCompletion)completion
 {
     assertChipStackLockedByCurrentThread();
-    MTR_LOG("BDX Transfer Session Data: %@: %@", fileDesignator, data);
+    MTR_LOG("BDX Transfer Session Data for log download: %@: %@", fileDesignator, data);
 
     auto * download = [_downloads get:fileDesignator fabricIndex:fabricIndex nodeID:nodeID];
     VerifyOrReturn(nil != download, completion([MTRError errorForCHIPErrorCode:CHIP_ERROR_NOT_FOUND]));
@@ -510,7 +510,7 @@ - (void)handleBDXTransferSessionEndForFileDesignator:(NSString *)fileDesignator
                                                error:(NSError * _Nullable)error
 {
     assertChipStackLockedByCurrentThread();
-    MTR_LOG("BDX Transfer Session End: %@: %@", fileDesignator, error);
+    MTR_LOG("BDX Transfer Session End for log download: %@: %@", fileDesignator, error);
 
     auto * download = [_downloads get:fileDesignator fabricIndex:fabricIndex nodeID:nodeID];
     VerifyOrReturn(nil != download);