`Sugg` structured snippet modifications wishlist

[oli-obk]

Our Sugg builder type has support for many code snippets, but in some cases we still fall back to strings. One such case is

rust-clippy/clippy_lints/src/needless_bool.rs

Lines 77 to 83 in 0a0792e

	format!("return {}", snip)
	} else {
	snip.to_string()
	};
	if parent_node_is_if_expr(&e, &cx) {
	hint = format!("{{ {} }}", hint);

There are probably more, but for now we should add methods for

• return $sugg (e.g. a return_expr method that wraps the current suggestion in a return call)
• blockifying (turns the current suggestion into a block where the current suggestion is the trailing expression)