* [HDS] Prep/cleanup steps for Highlighting the data source (#39681)

* Rename `DATA_BUCKET` key to `MODELS`

* Rename misleading method

`isSavedQuestionSelected` is too narrow because we can also have
other saved entities, such as models (and soon metrics) as the selected source.

* Fix type for `selectedTableId`

* Extract `sourceId`

* Rename saved question instances to saved entity

* Rename related components

* Show models correctly in the data source picker (#39686)

* Show models correctly in the data source picker

* Address review comments

* Destructure props

* Add E2E reproduction for #39699

* Prevent accessing potentially stale value

Closes #39699