[UPD] Enforce C++ version and improve setup.py flexibility

Context

1. C++-14

Fixes aidge_core#225 (closed) for aidge_quantization. The same update must be done on every module.

2. Python module compilation

Also increase 'setup.py' compilation option flexibility using environment variables. Made to work with aidge!97 (merged)

unit_tests/CMakeLists.txt

-Include(FetchContent)
+# Catch2 configuration
+set(CATCH2_MIN_VERSION 3.3.0)
 
-FetchContent_Declare(
-  Catch2
-  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
-  GIT_TAG        v3.0.1 # or a later release
-)
+# Try to find system installed Catch2
+find_package(Catch2 ${CATCH2_MIN_VERSION} QUIET)
 
-FetchContent_MakeAvailable(Catch2)
+if(NOT Catch2_FOUND)
+    message(STATUS "Catch2 not found in system, retrieving from git")
+    Include(FetchContent)
+
+    FetchContent_Declare(
+      Catch2
+      GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+      GIT_TAG        devel # or a later release
+    )
+    FetchContent_MakeAvailable(Catch2)
+    message(STATUS "Fetched Catch2 version ${Catch2_VERSION}")
+else()
+    message(STATUS "Using system Catch2 version ${Catch2_VERSION}")
+endif()
 
 file(GLOB_RECURSE src_files "*.cpp")