[Flang] Allow Intrinsic simpification with min/maxloc dim and scalar result (#81619)

This makes an adjustment to the existing fir minloc/maxloc generation
code to handle functions with a dim=1 that produce a scalar result. This
should allow us to get the same benefits as the existing generated
minmax reductions.

This is a recommit of #76194 with an extra alteration to the end of
genRuntimeMinMaxlocBody to make sure we convert the output array to the
correct type (a `box<heap<i32>>`, not `box<heap<array<1xi32>>>`) to
prevent writing the wrong type of box into it. This still allocates the
data as a `array<1xi32>`, converting it into a i32 assuming that is
safe. An alternative would be to allocate the data as a i32 and change
more of the accesses to it throughout genRuntimeMinMaxlocBody.