Makes use of fir.type_desc in order to delay the type desc address
resolution. The lowering inserts fir.type_desc operation instead of fir.addr_of
operation pointing to the fir.global type descriptor. The fir.type_desc
operation is then lowered in code gen to an address of operation in the LLVM
dialect. At this stage, the type descriptor is generated in all cases.
Reviewed By: vdonaldson
Differential Revision: https://reviews.llvm.org/D142920
16bd0fe56c