[BUG] vim freeze when there are too many files

[moetayuko]

Describe the bug

When the directory contains a large number of files (>5k in my experiments), launching coc-explorer will freeze vim entirely.

Result from CocInfo

(Obtained in another directory with fewer files, otherwise vim freezes and there's no way to run the command)

## versions

vim version: VIM - Vi IMproved 9.0 9000000
node version: v16.16.0
coc.nvim version: 0.0.81-2522eee5 2022-06-14 19:03:29 +0800
coc.nvim directory: /home/dianlujitao/.dotfiles/vim/.vim/plugged/coc.nvim
term: dumb
platform: linux

## Log of coc.nvim

2022-07-27T12:55:07.366 INFO (pid:3491417) [services] - registered service "languageserver.bash"
2022-07-27T12:55:07.417 INFO (pid:3491417) [services] - registered service "highlight"
2022-07-27T12:55:07.455 INFO (pid:3491417) [plugin] - coc.nvim initialized with node: v16.16.0 after 162ms
2022-07-27T12:55:07.638 INFO (pid:3491417) [attach] - receive notification: runCommand [ 'explorer', '--root-strategies', 'keep' ]
2022-07-27T12:55:07.689 INFO (pid:3491417) [attach] - receive notification: runCommand [
  'coc-helper.internal.didVimEvent_m1_v0_13_0_coc_helper_1',
  'BufDelete',
  2
]
2022-07-27T12:55:07.690 INFO (pid:3491417) [attach] - receive notification: runCommand [
  'coc-helper.internal.didVimEvent_m1_v0_13_0_explorer_2',
  'BufDelete',
  2
]
2022-07-27T12:55:08.215 INFO (pid:3491417) [attach] - receive notification: highlight []
2022-07-27T12:55:08.954 INFO (pid:3491417) [attach] - receive notification: highlight []
2022-07-27T12:55:10.959 INFO (pid:3491417) [attach] - receive notification: showInfo []

Steps to reproduce
Steps to reproduce the behavior:

1. mkdir test && cd test
2. touch {1..5000} or more files
3. :CocCommand explorer
4. Get your dead vim

Expected behavior

Vim works and files are properly listed in explorer's buffer