update project template

This allows us to use target_compile_features to set the C++ standard
in cppext and move to a newer standard.

Before boost child's terminate() was used, which send SIGKILL.
This can lead to remaining device nodes which are not cleaned up properly.

As the race condition only occurs on jenkins and is not reproducible, this is the attempt to improve something. The change should not make any difference, but the test should not hang in the first place, but does.

author fiveisgreen <4203265+fiveisgreen@users.noreply.github.com> 1733927785 +0100
committer fiveisgreen <4203265+fiveisgreen@users.noreply.github.com> 1737058259 +0100

refactor: Formal code cleaning

Implement linter suggestions
Both manual and automatic (fix-linter) alterations addressing linter
warnings.
Reverted fix-linter's renaming of getRegisterAccessor_impl to getRegisterAccessorImpl
back to getRegisterAccessor_impl, since the alteration won't compile,
and corresponding linter warnings are suppressed.
In SerialPort.cc, bit operations now only occur with uints
Change to size_t in SerialPort::send()
Eliminates C-style array in SerialPort::readline()
Satisfies the linter for the move semantics of the DummyServer::LockingString
constructor.

All .cpp files renamed to .cc
Consistent naming convention used.

As termios does not behave as expected it is switched to polling
to avoid random blocks.

As the race condition only occurs on jenkins and is not reproducible, this is the attempt to improve something. The change should not make any difference, but the test should not hang in the first place, but does.

This is a hack for focal, where the nlohman version is too old for inja.
We now implicitly assume that nlohmann is found because inja needs it.

This should be reverted once we don't have to support focal any more.

Reunderstoold the timeout and found no race condition there.

Debug prints outside of the DummyServer are removed

feat: DummyServer constructor has debug flag
All print-outs are under the debug flag

test: Has a dedicated test: testVoidWrite
test: Also has a 'hack' counter VoidType test in testCommandBasedBackendUnified

- always throw ChimeraTK::runtime_error instead of std::runtime_error
- catch the correct error

fix(project-template): (re-)enable DOT support in Doxygen