Use std::char_traits<char>::find instead of strnlen for better
portability.

* meson: run through muon's fmt to fix formatting

* meson: switch arrays to files

Allows muon to alphabetically sort files. switch headers back to arrays
as split() can only be used on strings.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

* Don't expose header windows.h in catch_all.hpp
* Fix generateAmalgamatedFiles.py

The Meson[1] build system makes it easier incorporate third-party
libaries into a project if they also build using Meson.

Let's add a minimal Meson build that's compatible with the CMake build,
along with a GitHub workflow to check that it builds and that at least
the simplest SelfTest runs.

The handling of catch_user_config.hpp is inspired by BUILD.bazel and
doesn't attempt to support any configuratons options. Such features
could be added later.

Meson strongly discourages using wildcards to specify sources, so the
source and header lists are copied from CMakeLists.txt.

Add a new test workflow to test the Meson builds. I was unable to get
these tests to pass with Ubuntu 20.04, so they use Ubuntu 22.04.

I'm neither a CMake nor a Meson expert, but the results seem to work for
me.

[1] https://mesonbuild.com/

Co-authored-by: Mike Crowe <mcrowe@brightsign.biz>

* Suppress clang-tidy *-avoid-c-arrays for TEMPLATE_TEST_CASE
* Made globalRegistrar `const` to avoid `cppcoreguidelines-avoid-non-const-global-variables`

Fixes #2095

Fixes #2520.