A command to discard autocompletion

[MaxVerevkin]

Sometimes I start going though the completion list using tab and then realize that I want to to go back and just continue from the state before I started tab-ing. I tried

[keys.insert]
C-x = ["normal_mode", "undo", "insert_mode"]

which didn't work (#8131). But even if it worked, I think a dedicated command would be better.

[the-mikedavis]

This should be a command on the completion component so I will close this in favor of #5505