Make swh services push their textual log records as json records

Currently only the bzr and git loader in staging are doing so.

plan:

• swh-apps: Reference new deps python-json-logger to their respective requirements.txt
  • swh-lister
  • swh-loader-cvs
  • swh-loader-svn
  • swh-loader-mercurial
  • swh-loader-package
  • swh-loader-savecodenow
  • swh-vault-cookers
  • swh-deposit-checkers
• Rebuild various impacted docker images (with the new deps)
• swh-charts: Bump new version of docker images
• staging: Check everything is fine ^
• Deploy to production
• swh-charts: Adapt chart so they can output json log records (only loader is able to currently)
  • lister
  • vault cookers
  • deposit checker
  • loaders
• Activate services ^ to log as json records
• Deploy in staging first
• Check everything is fine
• Deploy to production