[flang][runtime] Support non contiguous array in Finalize/Initialize (#67295)

Finalize/Initialize may be called on non contiguous arrays when dealing
with INTENT(OUT) dummies or non contiguous LHS. Update the related
element access to use indices instead of assuming contiguity and
manually computing the byte offset.

Also, the descriptor passed to parent type final routines should be set
to the parent type, otherwise descriptor.IsContiguous() may wrongfully
return true when finalizing parent components. Create a pointer to the
parent component when recursing in Finalize.