[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.cpp b/services/incremental/ServiceWrappers.cpp
index 144c466..dfe9684 100644
--- a/services/incremental/ServiceWrappers.cpp
+++ b/services/incremental/ServiceWrappers.cpp
@@ -166,6 +166,7 @@
     FileId getFileId(const Control& control, std::string_view path) const final {
         return incfs::getFileId(control, path);
     }
+    std::string toString(FileId fileId) const final { return incfs::toString(fileId); }
     std::pair<IncFsBlockIndex, IncFsBlockIndex> countFilledBlocks(
             const Control& control, std::string_view path) const final {
         const auto fileId = incfs::getFileId(control, path);