Make Graphs into editable files

Currently, graph views have no associated file, and can only be configured via the GUI.

I think it make sense if each graph was actually a file, like a canvas, but with the source text editable in the “Source View” mode.

This would allow configuring complex filters and groups much more easily. The standard GUI is fine for simple graphs, but my workflow includes many graphs with lots of filters and groups, and it can be hard to keep track of and edit them all in the tiny text box of the GUI.

It would also improve general parity with the rest of obsidian. For example, graphs can only be saved as bookmarks, so they can’t be searched for in the quick switcher, and the tab names of all graphs are simply “Graph View”. The fact that different graph configurations cannot be named outside of bookmarks makes it difficult to work with multiple graphs open in a workspace at once.