Make Parcoach generate a CMake package

It let third party projects find Parcoach through find_package (see here for a POC until this is merged and released).

Available components: Analysis, Instrumentation_C (if instrumentation was enabled), Instrumentation_Fortran (if instrumentation and fortran were enabled). They setup the following imported targets for a third party project:

• Parcoach::ParcoachCollDynamic_MPI_C
• Parcoach::ParcoachRMADynamic_MPI_C
• Parcoach::ParcoachRMADynamic_MPI_Fortran And the PARCOACH_BIN and PARCOACHCC_BIN variables pointing to the relevant executables.

For this I had to create 3 separate instrumentation library (one for the collective instrumentation in C, one for the RMA with the C overload, one for the RMA with the Fortran overload).

Since Parcoach can now be found, I also made the "standalone" tests use find_package to find Parcoach binaries/libraries.

To do before merging:

• remove the commit adding flang from the manifest (we can add it back when guix-hpc/guix-hpc!22 (merged) is merged.)