miqToolbarOnClick>getParams - use send_checked, simplify
miqToolbarOnClick>getParams - use send_checked, simplify

  * we no longer use `url_parms` to know when to send `miq_grid_checks`
    * before: when ending with `_div` and nonempty, or containing `id=LIST`
    * now: when `send_checked` and nonempty
    * change: `params[:miq_grid_checks]` will be `nil` instead of `""` when nothing is selected

  * we always call `miqSerializeForm` when ending with `_div`, but clean up nothings
    * before: when `_div` and empty
    * now: always, but returns `""` for GTLs
    * (but the alternative of sending when _div and not send_checked or empty is probably wrong anyway)

  * the ? url_params variant is handled a bit differently
    * `?` position
      * before: this would affect any url_parms containing a question mark
      * now: url_parms needs to start with it
      * but not seeing any url_parms values where this would matter
    * multiple `?`
      * before: split[1] pretty much means just anything between the first two question marks
      * now: slice(1) will use the whole string
      * but not seeing any url_parms values where this would matter

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic