LLVMFlang support and misc workarounds

Changed

• Update submodule (gFTL-shared)
• Update CI to have gfortran-10 and gfortran-11 only on ubuntu-22.04
• Update CI NVIDIA to NVHPC 24.7
• Add Flang to CI

Fixed

• Implemented a workaround for IFX in tests. Updated tests to use gFTL v2 while at it.

Added

• LLVMFlang compiler support