[zsh] Fix backslash escaping

Fix #3859

To test:

  FZF_CTRL_T_COMMAND="echo -E 'foo\bar\baz'; echo -E 'hello\world'"

  _fzf_compgen_path() {
    eval $FZF_CTRL_T_COMMAND
  }

  source shell/key-bindings.zsh
  source shell/completion.zsh

shell/completion.zsh

@@ -171,9 +171,9 @@ __fzf_generic_path_completion() {
             rest=${FZF_COMPLETION_PATH_OPTS-}
           fi
           __fzf_comprun "$cmd" ${(Q)${(Z+n+)fzf_opts}} -q "$leftover" --walker "$walker" --walker-root="$dir" ${(Q)${(Z+n+)rest}} < /dev/tty
-        fi | while read item; do
+        fi | while read -r item; do
           item="${item%$suffix}$suffix"
-          echo -n "${(q)item} "
+          echo -n -E "${(q)item} "
         done
       )
       matches=${matches% }

shell/key-bindings.zsh

@@ -52,8 +52,8 @@ __fzf_select() {
   local item
   FZF_DEFAULT_COMMAND=${FZF_CTRL_T_COMMAND:-} \
   FZF_DEFAULT_OPTS=$(__fzf_defaults "--reverse --walker=file,dir,follow,hidden --scheme=path" "${FZF_CTRL_T_OPTS-} -m") \
-  FZF_DEFAULT_OPTS_FILE='' $(__fzfcmd) "$@" < /dev/tty | while read item; do
-    echo -n "${(q)item} "
+  FZF_DEFAULT_OPTS_FILE='' $(__fzfcmd) "$@" < /dev/tty | while read -r item; do
+    echo -n -E "${(q)item} "
   done
   local ret=$?
   echo