Improve datasets graph UX

[bbovenzi]

We had a bunch of complicated logic trying to separate out unconnected dataset "graphs" from each other in the UI. It was buggy and could cause the UI to crash if there were too many datasets. So I decided to refactor a few things wih the tools I have available:

• Always render the full datasets dependencies graph
• Merge the Dataset and DAG search bars into one, with a single selection vs multiselect
• Can click to select a DAG
• Hover on a DAG shows popover to link to it's page
• Add loading indicator to the graph
• Zoom the graph to the node upon selection
• Highlight edges connected to a DAG
• Don't have the list/details left panel changing width when changing dataset selection

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