mass-scan: Run massive scan

We need to track the run of scans. These actual scans will be done in several batches. The initial batch of 500k projects will likely uncover necessary code updates and adjustments necessary for the remaining scans; each subsequent larger batch will likely uncover less, but some, cases that reveal the need for further fixes and improvements. The size in number of projects is a rough cut approach. Eventually SWH is file-based and has 20 to 30 Billion files.
We should track these tasks and issues:

- [ ] https://github.com/aboutcode-org/mass-scan/issues/13
- [ ] https://github.com/aboutcode-org/mass-scan/issues/14
- [ ] https://github.com/aboutcode-org/mass-scan/issues/15
- [ ] https://github.com/aboutcode-org/mass-scan/issues/16
- [ ] https://github.com/aboutcode-org/mass-scan/issues/17
- [ ] https://github.com/aboutcode-org/mass-scan/issues/18
- [ ] https://github.com/aboutcode-org/mass-scan/issues/19