F08 tests with lib2

Out of the tests in mpich-testsuite-4.3.0/f08/testlist, this is the status of lib2:

Test Category	Status
attr	❌ Fail
pt2pt	❌ Fail
coll	✅ Pass
datatype	✅ Pass
comm	✅ Pass
rma	❌ Fail
subarray	✅ Pass
topo	✅ Pass
ext	✅ Pass
info	✅ Pass
init	✅ Pass
io	✅ Pass
misc	✅ Pass
spawn	❌ Fail
timer	✅ Pass
profile	✅ Pass

• attr fails because we need to fully support a callback system that translates callbacks to C from the MPI implementation to callbacks in F08 from the application. Their signature is different so we cannot register Fortran callbacks in the MPI runtime using C calls. There is also the issue of Fortran and C registering attributes by void * or MPI_ADDRESS_KIND, with the latter having one less redirection.

• pt2pt2 testing fails but has not yet been explored

• rma testing fails but has not yet been explored

• spawn depends on MPI_Comm_spawn* which needs to be specially treated and it's probably easier to do it manually rather than with automatic code generation. Regardless, the translation to C has not yet been implemented in the spawn calls.