Watcher.subscribe might miss some of many fast subsequent changes

[cdietrich]

Originally reported as microsoft/vscode#220039

when we do a huge number of file changes then Watcher.subscribe might not always produce all events
and thus we miss relevant file changes

a reproducer can be found at https://github.com/cdietrich/parcel-watcher-bug

• on mac air m1 i can see it quite reliably
• on mac m2 pro less
• on linux mint (t480s) rarely but can be seen

[ocallesp]

This issue is impacting the Test Explorer in the C# Dev Kit Extension. Missing these events causes some tests to be skipped or not recognized properly, leading to a frustrating user experience. We already have a GitHub issue reported here: microsoft/vscode-dotnettools#996

It would be amazing if this could be looked into, as fixing it would really help improve the reliability of the Test Explorer.