dep: Add catch2 unit test framework and wire it up

To enable the test suite, make sure to configure CMake with -DBUILD_TESTING=1 , since it is disabled by default. The catch2 dependency will be downloaded during configure time.

Also add a new target "tests-common", which includes unit tests for the "common" project. To finally run the tests use the "test" target.

CircleCI: Run unit tests
(cherry picked from commit 6a28ee7b2a4269aa7e43265d1cd0067537e3e883)

tests/CMakeLists.txt

@@ -0,0 +1,23 @@
+# This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+#
+# This file is free software; as a special exception the author gives
+# unlimited permission to copy and/or distribute it, with or without
+# modifications, as long as this notice is preserved.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY, to the extent permitted by law; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+CollectSourceFiles(
+  ${CMAKE_CURRENT_SOURCE_DIR}/common
+  COMMON_SOURCES
+)
+
+add_executable(tests-common ${COMMON_SOURCES})
+
+target_link_libraries(tests-common
+  PRIVATE
+    common
+    Catch2::Catch2)
+
+catch_discover_tests(tests-common)