Fortran: remove obsolete compilers from default search list
Build systems generally search a list of compilers for a given language. For Fortran, CMake searches a list of compilers, some of which are long obsolete such as GCC 4. A better practice may be to search the currently maintained generic compiler names (that is, without version numbers). If a user wishes to specify an obsolete or specific compiler, they do so with environment variable FC or CMAKE_Fortran_COMPILER.
!7548 (merged) is an attempt at updating the default list to compilers most users would expect.
The philosophy is: for each supported Fortran compiler, search one generic high level name as per the vendor. For Intel compiler, because oneAPI LLVM "ifx" is still quite new, I left in the long-established "ifort" because it isn't yet deprecated, despite that being the long term Intel plan.