Feat: Separating metrics views and dashboards

[mindspank]

As Rill grows we want to separate out the metrics layer (view) from the dashboard. Today we mix visual dashboard UI properties with our metrics layer and as we add additional asset types it’s semantically cleaner for them to reference a metric view instead of a dashboard.

In addition a separation of metrics definitions from it’s dependent resources allows us to further promote reusability of the metrics definitions without having to duplicate them.

https://www.notion.so/rilldata/Metrics-Views-as-a-first-class-resource-in-Rill-1a5599f3129547d7ad7151785f4de223?pvs=4

[nishantmonu51]

@ericpgreen2 : We should plan this alongwith the File explorer changes.

[nishantmonu51]

Pushing it down a sprint in order to make room for Deploy journey improvements. Will plan the implementation along with Visual Metrics Editor.

[ericpgreen2]

Closed by #5724