Use `events` over `options` for internal events

What does this MR do and why?

Related to #427298 (closed)

All internal events metrics currently repeat the same data in options and events attribute. As a first step towards removing options, let's make it so that the metrics classes read the events attribute instead of the options attribute when possible.

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Before	After

How to set up and validate locally

1. Stay on master branch
2. Choose an internal_events metric with events: key, for example: g_project_management_issue_removed_from_epic_monthly
3. Trigger the event tracked by the metric for last week, for example: Gitlab::UsageDataCounters::HLLRedisCounter.track_event('g_project_management_issue_removed_from_epic', values: SecureRandom.uuid, property_name: 'user.id', time: 1.week.ago). You can repeat that multiple times.
4. Open the rails console and try to calculate the chosen metric, for example: Gitlab::Usage::ServicePing::InstrumentedPayload.new(['redis_hll_counters.issues_edit.g_project_management_issue_removed_from_epic_monthly'], :with_value).build. Since we triggered the event, this should return a non-zero value.
5. Checkout this MR's branch and reload! the console
6. Calculate the metric again: Gitlab::Usage::ServicePing::InstrumentedPayload.new(['redis_hll_counters.issues_edit.g_project_management_issue_removed_from_epic_monthly'], :with_value).build
7. This should return the same value as before.
8. Remove the options block from the metric (example: lines 12-14) and reload! the console again
9. Calculate the metric again. This should return the same value again.