[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/ServiceWrappers.h b/services/incremental/ServiceWrappers.h
index 4815caf..f2d0073 100644
--- a/services/incremental/ServiceWrappers.h
+++ b/services/incremental/ServiceWrappers.h
@@ -92,6 +92,7 @@
     virtual incfs::RawMetadata getMetadata(const Control& control, FileId fileid) const = 0;
     virtual incfs::RawMetadata getMetadata(const Control& control, std::string_view path) const = 0;
     virtual FileId getFileId(const Control& control, std::string_view path) const = 0;
+    virtual std::string toString(FileId fileId) const = 0;
     virtual std::pair<IncFsBlockIndex, IncFsBlockIndex> countFilledBlocks(
             const Control& control, std::string_view path) const = 0;
     virtual ErrorCode link(const Control& control, std::string_view from,