This change was tested with the following cases:
- Generate a summary for a core using an automatically detected or a given
kernel;
- Generate a summary for a core with a given dumpnr within the default or
a given core dump directory using an automatically detected or a given kernel;
- Generate a summary for a core compressed with gzip(1);
- Generate a summary for a core compressed with zstd(1);
- Generate a summary for a core and write it to a core.txt.# file;
- Verify if the -d flag and explicit vmcore are mutually exclusive;
- Verify if the -n flag and explicit vmcore are mutually exclusive.