EscherBSERecord fillFields() to return consumed bytes

[jmestwa-coder]

Summary

Restore the fillFields() contract in EscherBSERecord by returning the number of bytes actually consumed from the input stream rather than a reconstructed serialized size.

Problem

EscherBSERecord.fillFields() returned the embedded blip's getRecordSize(), which can differ from the number of bytes actually read when malformed records contain inconsistent size information.

This can cause parent containers to advance by an incorrect offset and mis-locate subsequent sibling records during parsing.

Fix

• Return the actual number of bytes consumed (bytesRead) when calculating the value returned by fillFields().
• Preserve the expected parser invariant that fillFields() reports consumed input bytes.

Test

• Add a regression test covering a malformed EscherMetafileBlip whose cbSave value exceeds the data declared by the record length.
• Verify that EscherBSERecord.fillFields() reports the record's actual on-disk length rather than an inflated reconstructed size.
• Demonstrate that the previous behavior would over-report consumed bytes and cause parser offset drift.

[pjfanning]

lgtm