[Proposal] - Improved data selector

[shanilpa]

Overview

The following proposal seeks to build on top of the previous improvements to the data selector: #4482. The improvements are being made to support connections to external data sources, allowing users to select connections, more quickly select recently selected data and allow access to an advanced selector for use cases where it is needed.

Related Issue

#6070
#6068

[paulstn]

What would the selection of multiple datasources look like a SQL JOIN? And would the combined datasource be saved as some reference? Without that extra step of saving a user-defined combined datasource, could users save queries in the first place?