[flang][runtime] Decouple scalar output APIs from descriptors (#92444)

For testing purposes the implementations of the output APIs like
OutputInteger32 have been simply constructing descriptors and executing
the operation through the general DescriptorIO template. This patch
decouples those APIs from that mechanism so that programs using simple
"PRINT *" statements for output can link to a smaller portion of the I/O
runtime support library. (This is the only form of I/O accepted in GPU
device code by previous CUDA Fortran and Fortran OpenACC compilers.)