Add Sisense snippet information to YAML files

Currently, we keep the information for building xMAU dashboards in sheetload.usage_ping_metrics_sections spreadsheet.

We could have this information in YAML files. And change there what should be added for a specific stage and group to a chart.

• Add a new attribute to metric yaml file proposed name xmau_metric_type
• xmau is one of umau, smau, gmau column that is in the spreadsheet
• xmau_metric_type is an array of enum values. The values could be one of gmau,smau,paid_gmau, umau, more values can be added in future.
• using the spreadsheet we can build a script to update the metric definitions. Looking at the columns smau, gmau, may, paid_gmau values TRUE/FALSE we add the values in YAML file.

I'll take 3 examples of how yaml would look like for 3 metrics

1. analytics_unique_visits.analytics_unique_visits_for_any_target

dashboard_types: ​[]

2. usage_activity_by_stage_monthly.plan.epics

dashboard_types:
- gmau
- paid_gmau

3. usage_activity_by_stage_monthly.release.deployments

dashboard_types:
- smau

Scenarios

Using information from table add related dashboard_types

smau	gmau	mau	paid_gmau	dashboard_type
TRUE	FALSE	FALSE	FALSE	[smau]
TRUE	TRUE	FALSE	FALSE	[smau, gmau]
TRUE	TRUE	TRUE	FALSE	[smau, gmau, mau]
TRUE	TRUE	TRUE	FALSE	[smau, gmau, may, paid_gmau]
...	rest of combinations

cc @gitlab-org/growth/product-intelligence @mpeychet_