* lisp/progmodes/sql.el: Try and avoid eval; use define-derived-mode

Remove redundant `:group` args.

(sql-interactive-mode-map): `set-keymap-parent` is always fboundp.
(sql-get-product-feature): Prefer `symbol-value` over `eval`.
(sql--adjust-interactive-setup): New function, extracted from
`sql-interactive-mode`.
(sql-interactive-mode): Use it and `define-derived-mode`.
(sql-connect, sql-connection-menu-filter): Prefer `cl-progv` over `eval`.

Author: monnier