Delete from command history by Key command

[yulog]

I read #554 and deleted my history. But history is as follows.

36 store:del-cmd 1
37 store:del-cmd 20
38 store:del-cmd 24
39 store:del-cmd 22
40 store:del-cmd 23
...

I want to delete directly from list (=Ctrl+R) with a keystroke such as Ctrl+Del.

[krader1961]

Note that this was requested in issue #554 but not implemented because the solution to that issue focused on the basic functionality. I would also argue that, since Elvish does not do duplicate command elimination, it makes more sense for a command history key binding to eliminate all instances of a command with the same character sequence rather than deleting a specific command sequence number as is done by store:del-cmd.