Add raw usage data table

What does this MR do?

• Add RawUsageData model
  • columns uuid(same every time, do we need it?), payload(jsonb), recorded_at, send_at(time we send it)
• Save raw_usage_data row
• Consider a doing this behind a feature flag?

Migration output

➜  rake db:migrate:up VERSION=20200803125340
== 20200803125340 CreateRawUsageData: migrating ===============================
-- table_exists?(:raw_usage_data)
   -> 0.0005s
-- create_table(:raw_usage_data)
   -> 0.0181s
== 20200803125340 CreateRawUsageData: migrated (0.0236s) ======================

rake db:migrate:down VERSION=20200803125340
== 20200803125340 CreateRawUsageData: reverting ===============================
-- drop_table(:raw_usage_data)
   -> 0.0086s
== 20200803125340 CreateRawUsageData: reverted (0.0157s) ======================

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #233360 (closed)