cgen: make char literals wide (#7769)

vlib/builtin/utf8_test.v

@@ -4,3 +4,11 @@ fn test_utf8_char_len() {
 	s := 'п'
 	assert utf8_char_len(s[0]) == 2
 }
+
+fn test_utf8_wide_char() {
+	r := `🌎`
+	val := r.str().str
+	unsafe {
+		assert '${val[0]:x}${val[1]:x}${val[2]:x}${val[3]:x}' == 'f09f8c8e'
+	}
+}