Improve UX of importing vs. opening files (#3661)

* wip

* fix drag and drop

* fix

* fix tests

* fix tests

* fix warning

* Partial code review

* add dialog

* fix web

* fix web

* push back release candidate expiry

* Code review

* Reduce code duplication for pasting files in frontend

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

editor/src/dispatcher.rs

@@ -571,10 +571,9 @@ mod test {
 				"Demo artwork '{document_name}' has more than 1 line (remember to open and re-save it in Graphite)",
 			);
 
-			let responses = editor.editor.handle_message(PortfolioMessage::OpenDocumentFile {
-				document_name: Some(document_name.to_string()),
-				document_path: None,
-				document_serialized_content,
+			let responses = editor.editor.handle_message(PortfolioMessage::OpenFile {
+				path: file_name.into(),
+				content: document_serialized_content.bytes().collect(),
 			});
 
 			// Check if the graph renders