wid-edit.el: Cosmetic changes

wid-edit.el: Cosmetic changes

* lisp/wid-edit.el: Use #' to quote function names.
(widget--simplify-menu, widget-echo-help): Explicitly specify the
lexenv to `eval`.
(widget-choose, widget-get-sibling, widget-setup, widget-field-find)
(widget-choice-action, widget-checklist-value-get)
(widget-radio-value-create, widget-radio-value-set)
(widget-radio-action, widget-editable-list-delete-at)
(widget-group-value-create, widget-choice-prompt-value): Use `dolist`.
(widget-convert): Hoist `(setq current` out of the ifs.
(widget-convert): Hoist `(setq keys` out of the if.
(widget-after-change): Hoist `(setq begin` out of the if.
(widget-default-completions): Use `cond`.
(widget-default-value-set): Hoist `goto-char` out of the if.
(widget-choice-action): Hoist `nth` out of the if.
(widget-checkbox-action): Hoist `widget-apply` out of the if.
(widget-editable-list-value-create): Hoist `car` out of the if.
(widget-editable-list-entry-create): Hoist `(setq child ...` out of the if.
(widget-documentation-link-action): Fold `if` into `cond`.
(widget-key-sequence-value-to-external): Use `key-parse`.
(widget-plist-convert-option, widget-alist-convert-option):
Hoist `(setq key-type` out of the if.

(cherry picked from commit 129bc91a2c9b7a6e314b4a5a4c60c266ca1cac0f)