Control key delegation does not work.

Describe the bug
A clear and concise description of what the bug is.

With vim.useCtrlKeys enabled and using vim.handleKeys to delegate some ctrl key combinations back to VSCode, vim.handleKeys setting has no effect. This is on Vim 1.10.2 using VSCode version 1.38.1. Mainly Ctrl-C and Ctrl-V is what I am trying to use.

"vim.handleKeys": {
    "C-a": false,
    "C-x": false,
    "C-c": false,
    "C-v": false,
    "C-s": false,
    "C-k": false,
},

To Reproduce
Steps to reproduce the behavior:

have vim.useCtrlKeys enabled and set some keys to revert to VSCode using vim.handleKeys.

Expected behavior

I expect Ctrl-C and Ctrl-V to work as they have been delegated back to VSCode.

Screenshots
If applicable, add screenshots to help explain your problem.
If remapping-related, please attach log output: https://github.com/VSCodeVim/Vim#debugging-remappings.

Environment (please complete the following information):

• Extension (VsCodeVim) version: 1.10.2
• VSCode version: 1.31.1
• OS: Windows 10 Pro x64

VSCode additional info:
Version: 1.38.1 (system setup)
Commit: b37e54c98e1a74ba89e03073e5a3761284e3ffb0
Date: 2019-09-11T13:35:15.005Z
Electron: 4.2.10
Chrome: 69.0.3497.128
Node.js: 10.11.0
V8: 6.9.427.31-electron.0
OS: Windows_NT x64 10.0.18362

Additional context
Add any other context about the problem here.

Start by reproducing the issue with vim.useCtrlKeys enabled and the shown vim.handleKeys settings, focusing on Ctrl-C and Ctrl-V in VSCode. Trace the key-delegation entry points for these settings; done means the configured combinations consistently reach VSCode instead of being handled by Vim.