[incremental] add last pending reads info in dumpsys

Example section of dumpsys output:
        lastPendingReads:
          fileId: 03300000000000000000000000000000
          metadataHex: 0330
          blockIndex: 857738
          bootClockTsUs: 166877488

Test: manual
BUG: 162600251
Change-Id: I37b04751c2a11972450ce7e9082116f8047e87df
diff --git a/services/incremental/test/IncrementalServiceTest.cpp b/services/incremental/test/IncrementalServiceTest.cpp
index 867312e..9b8cf40 100644
--- a/services/incremental/test/IncrementalServiceTest.cpp
+++ b/services/incremental/test/IncrementalServiceTest.cpp
@@ -294,6 +294,7 @@
     MOCK_CONST_METHOD2(getMetadata, RawMetadata(const Control& control, FileId fileid));
     MOCK_CONST_METHOD2(getMetadata, RawMetadata(const Control& control, std::string_view path));
     MOCK_CONST_METHOD2(getFileId, FileId(const Control& control, std::string_view path));
+    MOCK_CONST_METHOD1(toString, std::string(FileId fileId));
     MOCK_CONST_METHOD2(countFilledBlocks,
                        std::pair<IncFsBlockIndex, IncFsBlockIndex>(const Control& control,
                                                                    std::string_view path));