[Build] Align build to new aidge_core dependencies

Context

Simplify dependencies for binding and allow both TEST and PYBIND on. This aligns to the new aidge_core dependencies which are self-sufficient.

This change requires the installed aidge_core library to include the merge request aidge_core!187 (merged)

Modified files

• CmakeLists.txt: remove useless dependencies on pybind and fmt, fix file name of export build file, allow both TEST and PYBIND
• aidge_backend_cpu-config.cmake.in: add missing dependency on aidge_core
• cmake/PybindModuleCreation.cmake: minor fixes
• setup.py: add envvar AIDGE_BUILD_TEST=OFF|ON for building C++ tests
• unit_tests/CMakeLists.txt: minor change, prefer to use PRIVATE when linking final exe/module/library (no behavioral impact)

TODO

• Need first to merge in aidge_core: aidge_core!187 (merged)

cmake/PybindModuleCreation.cmake

 function(generate_python_binding pybind_module_name target_to_bind) 
-    add_definitions(-DPYBIND)
+
+    find_package(Python COMPONENTS Interpreter Development.Module)
+
     Include(FetchContent)
 
     set(PYBIND_VERSION v2.10.4)
-    set(PYBIND11_FINDPYTHON ON)
     message(STATUS "Retrieving pybind ${PYBIND_VERSION} from git")
 
     FetchContent_Declare(
@@ -12,14 +13,12 @@ function(generate_python_binding pybind_module_name target_to_bind)
         GIT_TAG        ${PYBIND_VERSION} # or a later release
     )
 
-    # Use the New FindPython mode, recommanded. Requires CMake 3.15+
-    find_package(Python COMPONENTS Interpreter Development.Module)
     FetchContent_MakeAvailable(PyBind11)
 
     message(STATUS "Creating binding for module ${pybind_module_name}")
     file(GLOB_RECURSE pybind_src_files "python_binding/*.cpp")
 
     pybind11_add_module(${pybind_module_name} MODULE ${pybind_src_files} "NO_EXTRAS") # NO EXTRA recquired for pip install
-    target_include_directories(${pybind_module_name} PUBLIC "python_binding")
-    target_link_libraries(${pybind_module_name} PUBLIC ${target_to_bind})
+    target_include_directories(${pybind_module_name} PRIVATE "python_binding")
+    target_link_libraries(${pybind_module_name} PRIVATE ${target_to_bind})
 endfunction()