tests can now be built as part of FSFW

This PR refactores the tests so they are built as part of the FSFW.
This is done by adding Catch2 with the FetchContent directive.

A future implementation might also use a system installation of Catch2
by first checking whether Catch2 can already be found as a package

The custom configuration folder testcfg was moved from the user folder
to the actual unittest folder.

The tests can be built by setting the CMake FSFW_BUILD_UNITTESTS option
to TRUE/ON. They are built with the static library and dropped inside
the build folders fsfw directory.

scripts/coverage.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*
+"""Small portable helper script to generate LCOV HTML coverage data"""
+import os
+import platform
+import sys
+import time
+import argparse
+from typing import List
+
+
+"""Copy this helper script into your project folder. It will try to determine a CMake build folder
+and then attempt to build your project with coverage information.
+
+See Unittest documentation at https://egit.irs.uni-stuttgart.de/fsfw/fsfw for more
+information how to set up the build folder.
+"""
+def main():
+
+    parser = argparse.ArgumentParser(description="Processing arguments for LCOV helper script.")
+
+    build_dir_list = []
+    for directory in os.listdir("."):
+        if os.path.isdir(directory):
+            os.chdir(directory)
+            check_for_cmake_build_dir(build_dir_list)
+            os.chdir("..")
+
+    if len(build_dir_list) == 0:
+        print("No valid CMake build directory found. Trying to set up hosted build")
+        build_directory = 'build-Debug-Host'
+        os.mkdir(build_directory)
+        os.chdir(build_directory)
+        os.system('cmake -DFSFW_OSAL=host -DFSFW_BUILD_UNITTESTS=ON ..')
+        os.chdir('..')
+    elif len(build_dir_list) == 1:
+        build_directory = build_dir_list[0]
+    else:
+        print("Multiple build directories found!")
+        build_directory = determine_build_dir(build_dir_list)
+    perform_lcov_operation(build_directory)
+
+
+def check_for_cmake_build_dir(build_dir_dict: list):
+    if os.path.isfile("CMakeCache.txt"):
+        build_dir_dict.append(os.getcwd())
+
+
+def perform_lcov_operation(directory):
+    os.chdir(directory)
+    os.system("cmake --build . -- fsfw-tests_coverage -j")
+
+
+def determine_build_dir(build_dir_list: List[str]):
+    build_directory = ""
+    for idx, directory in enumerate(build_dir_list):
+        print(f"{idx + 1}: {directory}")
+    while True:
+        idx = input("Pick the directory to perform LCOV HTML generation by index: ")
+        if not idx.isdigit():
+            print("Invalid input!")
+            continue
+
+        idx = int(idx)
+        if idx > len(build_dir_list) or idx < 1:
+            print("Invalid input!")
+            continue
+        build_directory = build_dir_list[idx - 1]
+        break
+    return build_directory
+
+
+if __name__ == "__main__":
+    main()