Change default doubleClickDelay to 500ms (from 300ms)

[emilykl]

Closes #8013 (see also original discussion in #6538)

Increase Plotly's default double-click delay to 500ms, to align with the most common OS defaults.

Steps for testing

1. Run the devtools dashboard and open any mock with a legend, for example legend_horizontal
2. Experiment with how fast you need to double-click a legend item in order to hide all other traces. If you double-click too slow, your clicks will be interpreted as single clicks and the clicked item will simply hide and then show again quickly
3. Do the same experimentation on main. Notice that the double-click speed threshold is noticeably slower on this branch compared to main.

[oscarrutt]

Thanks for at last for looking into this. However, as emilykl mentioned on another thread, on macOS the current setting for double-click delay is found by

% defaults read -g com.apple.mouse.doubleClickThreshold
0.5

So why can't Javascript run this command and read the output?

[emilykl]

@oscarrutt That's a shell command, so unfortunately there's no way to run it from JavaScript in the browser.

[oscarrutt]

@emilykl Thanks. I didn't know that. Most languages have some facility for that but I suppose JavaScript limits this for security. Thanks for your help on this little annoyance in Plotly.

[emilykl]

@oscarrutt Yeah, if we were running as a desktop app I think we'd be able to get this info but for security/privacy reasons, what's available in the browser is pretty limited.

Ultimately I think the most correct approach would be a refactor to use double-click event handlers, so we'll look into whether that's possible and feasible.