Add support for Cray, Fujitsu, and Intel ICX compilers

The following preprocessor macros are added:

- EIGEN_COMP_CPE and EIGEN_COMP_CLANGCPE version number of the CRAY compiler if
  Eigen is compiled with the Cray C++ compiler, 0 otherwise.

- EIGEN_COMP_FCC and EIGEN_COMP_CLANGFCC version number of the FCC compiler if
  Eigen is compiled with the Fujitsu C++ compiler, 0 otherwise

- EIGEN_COMP_CLANGICC version number of the ICX compiler if Eigen is compiled
  with the Intel oneAPI C++ compiler, 0 otherwise

All three compilers (Cray, Fujitsu, Intel) offer a traditional and a Clang-based
frontend. This is distinguished by the CLANG prefix.