[flang] Run-time derived type initialization and destruction

[flang] Run-time derived type initialization and destruction

Use derived type information tables to drive default component
initialization (when needed), component destruction, and calls to
final subroutines.  Perform these operations automatically for
ALLOCATE()/DEALLOCATE() APIs for allocatables, automatics, and
pointers.  Add APIs for use in lowering to perform these operations
for non-allocatable/automatic non-pointer variables.
Data pointer component initialization supports arbitrary constant
designators, a F'2008 feature, which may be a first for Fortran
implementations.

Differential Revision: https://reviews.llvm.org/D106297