s3: propagate storage rule fsync to volume server uploads (#10906)

The storage rule's fsync decision was computed by the filer
(detectStorageOption -> rule.Fsync) and applied on the filer's own HTTP
write path, but was never carried onto the chunk uploads S3 issues: the
AssignVolumeResponse had no fsync field, so the s3api client could not
learn the decision, and the chunked upload URL was hardcoded without it.
Every S3 write to a path with fsync configured went to the volume server
as a non-fsync write.

Carry the decision through the assign response:

- filer.proto: AssignVolumeResponse gains bool fsync, filled from the
  storage option the assign resolved.
- operation.AssignResult gains Fsync, so uploadChunk can append
  ?fsync=true to the volume server upload URL (single and replica
  fan-out paths).
- The S3 PUT/UploadPart assignFunc, the S3 copy path, the admin file
  browser upload, and the Iceberg worker assign functions all forward
  the response field.

Adds TestUploadReaderInChunksAppendsFsyncWhenAssigned.

weed/pb/filer_pb/filer_vtproto.pb.go

@@ -2944,6 +2944,16 @@ func (m *AssignVolumeResponse) MarshalToSizedBufferVT(dAtA []byte) (int, error)
 		i -= len(m.unknownFields)
 		copy(dAtA[i:], m.unknownFields)
 	}
+	if m.Fsync {
+		i--
+		if m.Fsync {
+			dAtA[i] = 1
+		} else {
+			dAtA[i] = 0
+		}
+		i--
+		dAtA[i] = 0x58
+	}
 	if len(m.Replicas) > 0 {
 		for iNdEx := len(m.Replicas) - 1; iNdEx >= 0; iNdEx-- {
 			size, err := m.Replicas[iNdEx].MarshalToSizedBufferVT(dAtA[:i])
@@ -7424,6 +7434,9 @@ func (m *AssignVolumeResponse) SizeVT() (n int) {
 			n += 1 + l + protohelpers.SizeOfVarint(uint64(l))
 		}
 	}
+	if m.Fsync {
+		n += 2
+	}
 	n += len(m.unknownFields)
 	return n
 }
@@ -17003,6 +17016,26 @@ func (m *AssignVolumeResponse) UnmarshalVT(dAtA []byte) error {
 				return err
 			}
 			iNdEx = postIndex
+		case 11:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Fsync", wireType)
+			}
+			var v int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return protohelpers.ErrIntOverflow
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				v |= int(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			m.Fsync = bool(v != 0)
 		default:
 			iNdEx = preIndex
 			skippy, err := protohelpers.Skip(dAtA[iNdEx:])