[ENG-9708] osfmetrics minus es6

[aaxelb]

Ticket

• ENG-9708

Purpose

remove all code using elasticsearch6 (now redundant after #11739 )

Changes

• remove es6 from settings, ci, and local dev setup
• remove es6 djelme classes from osf.metrics
• remove code that saves osfmetrics records to es6
• remove obsolete management commands:
  • migrate_osfmetrics_6to8
  • populate_impact_preprint_metrics
  • reindex_es6
• split osf.metrics.es8_metrics into osf.metrics.events, osf.metrics.daily_reports, osf.metrics.monthly_reports, osf.metrics.fields
• move utils from now-deleted osf.metrics.counted_usage into osf.metrics.utils
• rename FooEs8 to simply Foo
• improve "raw" metrics api:
  • pass client errors back to client (instead of 502)
  • remove /_/metrics/raw/ (instead use /_/metrics/raw-<djelme_backend_name>/ with backend name from settings)
• rename pytest mark es_metrics to djelme_elasticsearch_backends
• when gathering last month usage metadata, sum usage across all versions of a preprint
  • move versioned-osfid-formatting to GuidVersionsThrough.versioned_osfid(), for ease of reuse

Side Effects

QE Notes

CE Notes

Documentation

[felliott]

so much deletion, this is magnificent. APPROVE APPROVE APPROVE