perf: uv.spawn

[linrongbin16]

1. perf: async uv.spawn
2. add two provider types: "plain_list" and "command_list", so allow passing command lines in lua list, see:

   fzfx.nvim/lua/fzfx/config.lua

   Line 875 in 6e8524e

   provider = {

   . This is because uv.spawn only accept command lines in list format, see: How to pass command line string to uv.spawn？ luvit/luv#673.
3. fix sleep in live grep under Windows, Windows cannot use sleep 0.1 &&.