Add performance analytics metrics api

What does this MR do and why?

Add performance analytics metrics api for group level and project level.

note: This MR is behind performance_analytics feature flag, which is disabled by default.

related to #1884 (closed)

How to set up and validate locally

1. In rails console enable feature flag

   Feature.enable(:performance_analytics)

2. fetch api through curl

   > # Daily
   > curl -H 'Private-token: XXX' "http://local.gitlab.test:3000/api/v4/groups/134/performance_analytics/metrics?metric=issue_created&start_date=2022-09-01&end_date=2022-09-02"
   [{"date":"2022-09-01","value":1},{"date":"2022-09-02","value":0}]
   
   > # Monthly
   > curl -H 'Private-token: XXX' "http://local.gitlab.test:3000/api/v4/groups/134/performance_analytics/metrics?metric=issue_created&start_date=2022-09-01&end_date=2022-10-30&interval=monthly"
   [{"date":"2022-09","value":1},{"date":"2022-10","value":0}]
   
   > # All
   > curl -H 'Private-token: XXX' "http://local.gitlab.test:3000/api/v4/groups/134/performance_analytics/metrics?metric=issue_created&start_date=2022-09-01&end_date=2022-10-30&interval=all"
   {"value":1}

MR acceptance checklist

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