showQuickPick in onDidDeleteFiles doesn't work for multiple deleted files

[ws93]

• VSCode Version: Version: 1.44.2 (user setup)
  Commit: ff91584
  Date: 2020-04-16T16:36:23.138Z
  Electron: 7.1.11
  Chrome: 78.0.3904.130
  Node.js: 12.8.1
  V8: 7.8.279.23-electron.0
  OS: Windows_NT x64 10.0.18363
• OS Version: OS: Windows_NT x64 10.0.18363

Steps to Reproduce:

1. Clone my template extension project: https://github.com/ws93/deletefilesapi (The 4-line code I added after yo code)
2. npm install and then run extension
3. open a folder that contains multiple files
4. ctrl select 2 files and right click and delete them
5. I expect to see 2 quickpickers one by one. But instead, it seems the extension cancelled the first quick pick popup and only shows the second one. The selected item for first quickpicker is undefined.

There's also an issue #86210 with onDidDeleteFiles api that if you ctrl select multiple files and delete them, it will trigger onDidDeleteFiles multiple times instead of having one FileDeleteEvent that contains an array of multiple deleted files.

So I'm not sure if the problem is when the second event got fired it also fired a cancel or esc so it cancelled the first showQuickPick.

Does this issue occur when all extensions are disabled?: Yes

[isidorn]

This is the same underlying reason as #86210
Once we tackle that, we can look into this one. Until then assigning to backlog.