The group 'license' was renamed to 'provision'

  - Use milestone <13.9 for metrics definitions
  with no milestone defined

Add new category and data_source "license".

Correction:
Move license_trial_ends_on to ee

This adds `data_source: system` for metrics whose data comes from the
underlying operating system. Also, moves a few setting metrics that were
in the wrong metric subfolder and fixes some `value_type` entries.

  - Import metrics from events dictionary
  and usage ping
  - Metrics are set with skip_validation
  - Generate dictionary
  - Change value formatter, accept nil values
  - Fix naming in descriptions
  - Update initial metrics name with timestamp