Event numbers don't add information to the search: if you knew the
event number you wouldn't be searching for the command. Add an option
to remove them from the search to declutter it. Default it to true to
preserve the current behaviour.
ZSH_FZF_HISTORY_SEARCH_FZF_ARGS and
ZSH_FZF_HISTORY_SEARCH_FZF_EXTRA_ARGS may contain multiple arguments
separated by spaces that need to be expanded to build the command line
for fzf. This is currently done by calling a subshell and letting
echo handle it.
Unlike other shells, zsh does not do word splitting by default.
According to zshexpn(1) you can perform word splitting using the rules
for SH_WORD_SPLIT by using the ${=spec} construct. Avoid creating a
subshell and just expand the spaces.
