Assistant Builder: Tree component for datasources

[PopDaph]

Description

This PR implements the new Tree view in the Assistant Builder, as part of https://github.com/dust-tt/decisions/issues/164

To be tested on Front Edge: https://front-edge.dust.tt/

To be able to build a Tree view, each connector has been updated to expose a function retrieving the ContentNodes linked to a list of internalIds.

There's now a single button to manage all datasources selection (as opposed to a button to add a new, and 2 buttons per connection to edit or remove the selection).

Here are the changes in the PR:

• We're calling connector getContentNodes over getResourcesTitles to retrieve the content associated to the internalIds saved on the AssistantBuilderConfiguration. That means everywhere we now deal with ConnectorNode[] over Record<string, string>.
• Edit the "Add datasource modal" to be a "Manage selection modal".
• As we don't have a remove button anymore, the "unselect all" with untick all selected resources and if we save with nothing it removes the provider from the selected ones.
• Display the selected datasources as a Tree.

We discussed it IRL so I implemented as discussed but I still think that it will be confusing for users that we display the list of selected items not taking into account that an item is also selected by a parent selection.

PRs related to this change (no need to look at them, linked for posterity if needed someday):
#4031
#4044
#4050
#4083
#4084
#4118
#4119
#4122
#4125
#4132
#4134
#4136
#4138
#4139

Risk

Easy to rollback until we remove the getResourcesTitles connector route.

Deploy Plan

Nothing special, just deploy front.