Allow focused dashboard selection for DBSQL exporter (WIP)

[nfx]

[nfx]

as one of the action items of making DBSQL exporter more mature, we have to:

1. Make proper SDK for every DBSQL entity. json.RawMessage and map[string]any are not good at all to work in a scalable way.
2. figure out the "import a use-case" path, not only "code generate the entire manual workspace"

[pietern]

@nfx Some of the fields need those types, because they are arbitrary JSON blobs for which we don't have a stable schema.

[alexott]

superseded by #1788