pylint #105337 Custom report output-format [validation pending]

Allowing output-format to be a fully-qualified Python class name, such as "mypackage.mymodule.CustomReporter" so that a custom class can be used to format reports.

prioritynormal
typeenhancement
done in0.26.0
load left0.000
closed by#b43ad9e4c3ee minor tweaks to previous changeset (custom reporter). Closes #105337