Remove fetching Catch2 and Fix #163

[olivier-stasse]

Description

This PR fixes the fetching problem with Catch2.
It detects the Catch2 version and adapt the header inclusion.
If needed this can be refined in testing more precisely the version.
The CMakeLists.txt is simplified, and has a low impact in the code.

How I Tested

To test I added the rolling and the humble workflow to verify that both tests are feasible.

Do not merge before

• link to dependent pull request

I fulfilled the following requirements

• All new code is formatted according to our style guide (for C++ run clang-format, for Python, run flake8 and fix all warnings).
• All new functions/classes are documented and existing documentation is updated according to changes.
• No commented code from testing/debugging is kept (unless there is a good reason to keep it).

[nim65s]

Suggested change

	add_definitions(-DFOUND_CATCH2_MAJOR_VERSION=${Catch2_VERSION_MAJOR})
	if(Catch2_FOUND)
	add_definitions(-DFOUND_CATCH2_MAJOR_VERSION=${Catch2_VERSION_MAJOR})
	else()
	include(FetchContent)
	FetchContent_Declare(
	Catch2
	GIT_REPOSITORY https://github.com/catchorg/Catch2.git
	GIT_TAG v3.6.0)
	FetchContent_MakeAvailable(Catch2)
	add_definitions(-DFOUND_CATCH2_MAJOR_VERSION=3)
	endif()

I don't see the point in removing the fetch part