Visibility of InfraDev issues and work stream type allocations



Based on the recent discussions in Engineering Allocations, the goal is to track `infradev` issues on age per product groups. From @sloyd 

>>>
We need to clear up the delineation of Corrective Actions vs infradev escalations as they aren’t the same, yet there is also overlap. 
>>> 

@andrewn also has done weekly reports in this in https://gitlab.com/gitlab-org/infradev-reports/-/issues/5#summary-by-severity 

### To-DO
- [x] Create Central Eng Metrics for S1 Open Age, S2 Open Age & Table
  - https://app.periscopedata.com/app/gitlab/798401/Infrastructure-Embedded-Dashboard
- [x] Create Infradev Summary Dashboard with Filters
  - https://app.periscopedata.com/app/gitlab/899982/InfraDev
- [x] add metric for # of related incidents of infradev issues to match what gets shown in Andrew's infradev report
  - tracking in https://gitlab.com/gitlab-com/www-gitlab-com/-/issues/12226

### Requirements

* Create a new filterable equivalent dashboard similar to [corrective actions](https://app.periscopedata.com/app/gitlab/787921/Corrective-Actions) but only honed in for infradev
* Key charts:
  * Past due infradev
  * Average age of open infradev
  * Ability to view as a holistic view that can drill down to each product groups
* We need to be able to see how each product teams are doing and if they are able to keep up. 
* Lean on our philosophy of measuring open things


### Examples of the key charts 

![Screen_Shot_2021-08-04_at_6.33.33_AM](/uploads/8a2210a7f573cdfe87621b7cdbb7fafa/Screen_Shot_2021-08-04_at_6.33.33_AM.png)
   

## Plan 
* We are aligned on the metric `Open InfraDev Age`. This aligns with other Eng PIs (OMA, OBA, Open UX Debt Age) Reasons:
  * As a long-term indicator, provide a measure that captures the total effort. Average Age of Open achieves this, we give credit to efforts when any open issue is fixed
  * Give agency to each team to prioritize what is most severe, a recent infradev S2 may need action now than an older infradev S2 (example from this https://gitlab.com/gitlab-org/gitlab/-/issues/333184) 
  * Facilitate a 2 way direction of recognizing completed efforts and feedback loop. e.g. 
    * A product group team is doing well if `Open InfraDev Age` is going down.
    * A product group team needs help if `Open InfraDev Age` is going up.
    * Slice this by severity
  * This negates the complication of restarting SLOs when severity shifts, we set teams to focus on burning down infradev in each severity as one bucket. The first being S1 and S2 which is the agreed on path from the last meeting.
* @davis_townsend to create:
  * Open InfraDev Age S1 chart (add total number of issues in the backdrop)
  * Open InfraDev Age S2 chart (add total number of issues in the backdrop)
* @lmai1 to add a table at the end showing list of Open infradev issues (S1/S2)
* @lmai1 will ensure the handbook dashboard structure is accurate https://gitlab.com/gitlab-com/www-gitlab-com/-/issues/12154 
* This dashboard https://app.periscopedata.com/app/gitlab/798401/Infrastructure-Embedded-Dashboard is filterable down to every stage and group and is in our handbook dashboards https://about.gitlab.com/handbook/engineering/metrics/dev/create/#infrastructure-indicators
  * This will provide visibility into each teams and if we need to dial up more
* Separately we already have types of MRs merged per stage/group in the Development Indicators section of the same pages
  * This will tell us what type of work needs to increase/decrease
  * ![Screen_Shot_2021-07-29_at_12.25.35_PM](/uploads/a5016302b997c47c4afffa93dce6ffcc/Screen_Shot_2021-07-29_at_12.25.35_PM.png)
* We aim to have this in by next Engineering Allocation meeting.

![Screen_Shot_2021-08-02_at_1.18.55_PM](/uploads/20af37bc74625662ff7bd094244a0f7c/Screen_Shot_2021-08-02_at_1.18.55_PM.png)

### Dashboards 

Main entry point https://about.gitlab.com/handbook/engineering/metrics

cc @lmai1 for your visibility as this may also come up for development analytics

Story points: 5.0