Given the long run times, make ol-dumps easier to test

[cclauss]

Closes #5893

Testing (stats as of November 2021):
The oldump cron job on ol-home0 takes 18+ hours to process 192,000,000+ records in 29GB of data!!

These changes enable scripts/oldump.sh to OLDUMP_TESTING=true which will allow the script and openlibrary/data/dump.py to only process the first 1 million lines of the file instead of 192+ million lines. The first step of this script will still take 110 minutes to extract the 29GB of data from our database so it is highly recommended to save a copy of data.txt.gz to skip that step and accelerate the testing of subsequent job steps.

Technical

Call flow:
docker-compose.production.yml defines `cron-jobs` Docker container.
--> docker/ol-cron-start.sh sets up the cron tasks.
    --> olsystem: /etc/cron.d/openlibrary.ol_home0 defines the actual job
        --> scripts/oldump.sh
            --> scripts/oldump.py
                --> openlibrary/data/dump.py

Testing

Technical

Testing

Screenshot

Stakeholders

[cclauss]

Use Linux logger to write start and finish messages into the system log.

[mekarpeles]

changes lgtm, I committed a trivial fix to a lint/whitespace issue
Error: The process '/opt/hostedtoolcache/Python/3.9.9/x64/bin/pre-commit' failed with exit code 1

ty @BharatKalluri for helping w/ this code review!