fix: logging level for parsing potential PE files

[kzantow]

While looking in to an issue that a library parsing DotNET Portable Executables was writing to stdout, I noticed a number of warnings show up, for example, running:

syft --platform windows/amd64 registry:mcr.microsoft.com/windows/servercore:ltsc2019

Resulted in:

 ✔ Parsed image                                                                                           sha256:c632661e39bb365cf34bfdd943baa4ce5ba1ebdd713d790d1af0b9da20ae0bea
 ✔ Cataloged packages              [4566 packages]  
[0084]  WARN cataloger failed cataloger=dotnet-portable-executable-cataloger error=unable to parse PE file: DOS Header magic not found location=/Files/Windows/WinSxS/x86_microsoft
[0084]  WARN cataloger failed cataloger=dotnet-portable-executable-cataloger error=unable to parse PE file: DOS Header magic not found location=/Files/Windows/WinSxS/x86_microsoft
[0084]  WARN cataloger failed cataloger=dotnet-portable-executable-cataloger error=unable to parse PE file: DOS Header magic not found location=/Files/Windows/WinSxS/x86_microsoft

This PR adjusts the warnings to DEBUG level, e.g. nothing is printed by default but using the -vv option, you'd see:

...
[0083] DEBUG unable to parse PE file '/Files/Windows/WinSxS/x86_microsoft-windows-d..s-commandline-tools_31bf3856ad364e35_10.0.17763.1_none_5c764e9c11f85b2a/dsquery.exe': DOS Header magic not found
[0083] DEBUG unable to parse PE file '/Files/Windows/WinSxS/x86_microsoft-windows-d..s-commandline-tools_31bf3856ad364e35_10.0.17763.1_none_5c764e9c11f85b2a/dsrm.exe': DOS Header magic not found
...

We can see that these are just .exe files, many of which are not portable executables, so we really shouldn't be warning about them.

[wagoodman]

I think even the debugs should be trace logs though, since the given input is not guaranteed to be a PE file at all