fix: update apport coredump path handling for CorefileFinder

[Meetesh-Saini]

Apport uses the executable's pathname in the core filename. This update modifies the implementation to use the absolute path of the executable and replace both / and . with _ in the pathname to match apport's implementation.

[peace-maker]

Thank you! Do you have a link to the source or docs you used? Please add it to the code too so we can monitor for future changes if this wasn't the default behavior before.