[flang] Fix semantic checks for MOVE_ALLOC (#77362)

The checking of calls to the intrinsic subroutine MOVE_ALLOC is not
insisting that its first two arguments be whole allocatable variables or
components. Fix, move the code into check-calls.cpp (a better home for
such things), and clean up the tests.

Fixes https://github.com/llvm/llvm-project/issues/77230.