[flang][hlfir] Array constructor lowering [part 4/4]

Enable character and derived type array constructor lowering.
Nothing special needs to be done other than lowering the types
before the array constructor lowering.
Derived type are forced to use the runtime for now to avoid
undesired usage of user defined assignment that hlfir.assign
may trigger when using the runtime.

Differential Revision: https://reviews.llvm.org/D144548