Add computation of hashes of PE files excluding their overlay

At present, `retdec-fileinfo` computes hashes of the whole file:
```
Input file : test.exe
CRC32 : cdfbdc96
MD5 : 6e528dafa58c6c06fccfddd5f7ee715d
SHA256 : 000b1f22029c979c27c7310712cae66b8ade37378023487277ad7c86d59a34f6
```
In terms of PE files, this also includes overlay (provided that the file has an overlay). It might be useful to also compute hashes of PE files excluding overlay. Thus, two files that only differ by their overlay would have the same hash. This could be used to detect whether two files are identical except for their overlay.

Start by locating the retdec-fileinfo implementation that reports CRC32, MD5, and SHA256 for input files, then inspect how PE structure and overlay boundaries are identified. Done means PE files also have hashes computed without their overlay, so files differing only in overlay produce matching values; add or update coverage for this behavior if the existing test layout reveals a suitable place.

Written by the indexing model from the issue text.