Do not block dashboard SO loading on default data view loading

[flash1293]

In

kibana/src/plugins/dashboard/public/application/hooks/use_dashboard_app_state.ts

Line 148 in 00c8cf9

const isEmpty = await isDashboardAppInNoDataState(dataViews);

and

kibana/src/plugins/dashboard/public/application/hooks/use_dashboard_app_state.ts

Line 154 in 00c8cf9

const defaultDataView = await dataViews.getDefaultDataView();

first, the request is done to check whether there is data. Then, the default data view is loaded to check whether a default data view exists. Only afterwards the dashboard saved object is loaded. The data view loading is two roundtrips to Elasticsearch. The dashboard SO loading is one roundtrip to Elasticsearch. Loading these three things in parallel would save at least two roundtrips and speed up the time to meaningful render.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)