Reset partial key sequence on click / scroll

If you have the default leader key of `<space>`, and press `<space>` then click on something, the original `<space>` is still "stored" and will affect the result of the next key press. e.g. it'd just be a single `<space>` to open the `:tab ` commandline.

This is not very intuitive, so we should just reset a partial key sequence if you click, or scroll. This also matches the behaviour of (neo)vim.