Create process to compare processed/unprocessed reports

[preaction]

We need a process that can tell us which, if any, reports (test_reports / CPAN::Testers::Schema::Result::TestReport) have not yet been processed into a report summary (cpanstats / CPAN::Testers::Schema::Result::Stats).

The process should write the IDs of all the test reports that do not have a corresponding summary row, one per line.

In the future, the output of this process could be piped through xargs to the CPAN::Testers::Backend::ProcessReports program to process the missing reports.