[test][components] Use constexpr and is_detected

Closes #1208

See merge request !3360

[installexternal] Do some safety checks on tar archives using TarSafe

Closes #1207

See merge request !3361

[fmt] Update shipped version to 9.1.0

See merge request !3362

In C++20 mode passing non-constexpr format string yields a compiler
error. In that case, we have to use vformat(varstr, std::make_format_args(a, b, c...))

[bin][postprocessing] add pvpython version check for 5.11

See merge request !3355

remove ".git" with endswidth check rather than rstrip

See merge request !3359

[cleanup] [test][md][stokesdarcy][1p2c] remove unused properties_stokes.hh

See merge request !3356

[test][stokes] Add stabilized Box-Box donea test

See merge request !3350

[rans] Allow for more general solution types in addDynamciwWallProps

See merge request !3351

In coupled models we might pass some proxy solution generated by partial.
This is tested in the dumux-course example.

Feature/cvfe improvements

See merge request !3349

Delete obsolete COPYING symlink

See merge request !3348

This was meant to be for Debian packages. We do not have Debian packages to date.
Debian updated the way copyright information is supplied: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/

[license][authors] Simplify LICENSE.md file to only contain license

See merge request !3347

* Remove statement duplicated from README.md
* Move contributors to a separate file AUTHORS.md
* Mention AUTHORS.md file in the README.md

[readme] Explicitly mention bug reports and how to report security vulnerabilities

See merge request !3346