Patch 2/3 of the transition step 1 described in
https://discourse.llvm.org/t/rfc-enabling-the-hlfir-lowering-by-default/72778/7.
All the modified tests are still here since coverage for the direct
lowering to FIR was still needed while it was default. Some already have
an HLFIR version, some have not and will need to be ported in step 2
described in the RFC.
Note that another 147 lit tests use -emit-fir/-emit-llvm outputs but do
not need a flag since the HLFIR/no HLFIR output is the same for what is
being tested.
The implied-do index value has 'index' type, and it has to be
converted to the original ac-do-variable's data type.
Reviewed By: jeanPerier
Differential Revision: https://reviews.llvm.org/D150150
