mapping control-something to escape in insert doesn't work

[kyazdani42]

Describe the bug
Hi,
in insert mode, mapping C-something to Esc doesn't work properly.
when typing, you need to wait for 1/2 seconds before pressing the keys, else it produces an output like that:

Remapper: debug: trying to find matching remap. keys=a,<C-j>,<C-j>,<C-j>,<C-j>,<C-j>,<C-j>,<C-j>,<C-j>,<C-j>. mode=Insert. keybindings=insertModeKeyBindingsMap.

and cannot match the appropriate behavior. Tested with <C-j> and <C-e>
<C-c> and <C-[> work fine though. It also works perfectly in visual mode

To Reproduce
in settings.json:

{
    "keyboard.dispatch": "keyCode",
    "vim.debug.loggingLevelForConsole": "debug",
    "vim.insertModeKeyBindings": [
        {
            "before": ["<c-j>"],
            "after": ["<Esc>"]
        }
    ],
    "vim.visualModeKeyBindings": [
        {
            "before": ["<c-j>"],
            "after": ["<Esc>"]
        }
    ]
}

Expected behavior
mapping c-something to escape in insert mode should properly be detected

Environment (please complete the following information):

• Extension (VsCodeVim) version: 1.10.2
• VSCode version: 1.38.0
• OS: Linux 5.2.11-1-MANJARO x86_64
• I also use Xmodmap to map caps lock to control but that shouldn't affect this as it worked fine with mapping caps lock to escape before

[kyazdani42]

duplicate of #3530