chore: Use find_package in CMake, fallback to FetchContent

Context

Fix #205 (closed)

Use Cmake find_package() to find packages installed on system (namely fmt and Catch2), and fallback to using fetch_content() if the packages are not found. The main objective of this is to reduce build times.

Modified files

• CMakeLists.txt and UnitTests/CMaeLists.txt

unit_tests/CMakeLists.txt

-Include(FetchContent)
+find_package(Catch2 3.7.1)
 
-FetchContent_Declare(
-  Catch2
-  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
-  GIT_TAG        v3.0.1 # or a later release
-)
+if(NOT Catch2_FOUND)
+    message(STATUS "Catch2 not found in system, retrieving from git")
+    Include(FetchContent)
 
-FetchContent_MakeAvailable(Catch2)
+    FetchContent_Declare(
+      Catch2
+      GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+      GIT_TAG        v3.7.1 # or a later release
+    )
+
+    FetchContent_MakeAvailable(Catch2)
+endif()
 
 file(GLOB_RECURSE src_files "*.cpp")