Execute commands not handled by controllers when opening large notebooks

[DonJayamanne]

• Create a large notebook 1000 cells
• Open using VS Code API
• Wait for the promises
• Verify the notebook is active (via code)
• Select a controller via vs code commands API Verify the selection changed event is fired in the controller (i.e. controller is definitely selected)
• Run cells via the vs code commands API Bug: Nothing happens, controller does not get the cells to be executed.

Observations:

• UI is still loading the notebook.
• Hence it seems as though command handlers are not wiredup/not handled until the notebook UI completely loads

Not a bug, but a debt item to polish (there might be some code in the renderer thats slow to wireup the command handlers). As tests written need to work around these issues.

[rebornix]

@DonJayamanne can you please try to reproduce with logs, by F1 -> Set Log Level, change it to Trace, and then try to open the notebook. Once the notebook opens, in the Window output channel, you can find a trace like

2024-04-25 13:23:18.710 [trace] [NotebookEditor] open notebook perf file:///c%3A/Users/rebor/Code/Work/vscode/.vscode/notebooks/my-endgame.github-issues - extensionActivation: 15, inputLoad: 17, webviewComm: 17, customMarkdown: 521, editorLoad: 525

Which can tell use where the time is spent. Thanks!