vec_match() should only use incomplete propagation with "data.frame"s

[DavisVaughan]

i.e. with rcrd types that have a data frame proxy, it should require fully missing rows to be considered missing

> x <- new_rcrd(list(x = c(1, NA), y = c(NA_real_, NA_real_)))
> vec_match(x, x, na_equal = FALSE)
[1] NA NA
> vec_detect_complete(x)
[1]  TRUE FALSE

In this case, element 1 should still match, while element 2 should propagate an NA

This probably requires calling vec_detect_complete() up front on needles in the na_equal = FALSE case. Then replacing this dict_is_missing() call with if (!v_complete[i])

vctrs/src/dictionary.c

Line 442 in 173efaf

if (dict_is_missing(d_needles, i)) {