CMake >= 3.20: Scalapack find/build more robust

Changes to MUMPS and Scalapack to work in more situations correctly.

Require CMake >= 3.20 (and test 3.20 in CI) to help packaging robustness across platforms.

MUMPS 5.7.3 upstream. MUMPS_parallel option

option parallel (default on) is now option MUMPS_parallel

MUMPS upstream 5.7.3

Full Changelog: v5.7.2.0...v5.7.3.0

Upstream MUMPS 5.7.2. MKL detection improvements, C++ bugfix

correct Scalapack Git commit hash for scalapack build

BUGFIX for macOS with Clang, and other case-insensitive systems with C++ main programs using MUMPS via FetchContent or as Git submodule with add_subdirectory():
include ${mumps_SOURCE_DIR}/src, NOT ${mumps_SOURCE_DIR} to avoid MUMPS top-level file VERSION breaking build.

This was triggered when macOS Xcode headers became C++20 default.

MUMPS 5.7.1. General build system fixes

• also works with Visual Studio generator now. We separated C and Fortran targets to do this. Thanks for idea @dariomangoni
• corrected CMake logic for various cases and added CI case thanks @dariomangoni for pointing problems out and suggestions

Upstream MUMPS 5.7.0. Correct intsize64 for non-oneAPI. Arbitrary upstream version

• Default MUMPS upstream 5.7.0. See MUMPS User guide for various improvements.
• MUMPS 5.7.0 allows build without Scalapack cmake -Dscalapack=no
• Correct intsize64=on for non-oneAPI. Requires ALL libraries including MPI be compiled for 64-bit.
• Arbitrary MUMPS_UPSTREAM_VERSION download from mumps-solver.org

bugfixes, store MUMPS source outside of build dir

store upstream source outside of build directory -- allows flipping between MUMPS versions without redownloading source each time, which can be quite slow due to server / internet bandwidth

remove MUMPS source code download timeout

remove GNU Octave to save maintenance burden

test: use TEST_LAUNCHER (better practice in CMake)

tests default on if top level project

bugfix: GEMMT: was broken several months ago, now fixed

FindSCALAPACK: Correct Lapack alias with MKL

v5.6.2.2

FindSCALAPACK: correct ALIAS of Lapack with MKL

user-set CMAKE_TLS_VERIFY (default on)

• allow user-set CMAKE_TLS_VERIFY (default on)
• scalapack v2.2.1.6 (autobuild lapack if needed)

MUMPS 5.6.2. Autobuild scalapack if missing.

Ease building for users by auto-building Scalapack if missing.

CMake >= 3.19 required. Improve Find[SCA]LAPACK with MKL

For those using MKL match library to provide LAPACK and SCALAPACK, we now use Intel's MKLConfig.cmake as recommended. For those using MKL, MKL 2021.3 or newer is required.

CMake >= 3.19 required to avoid vendoring so much much code and to remove workaround logic.