[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