tests: add proper catch2 handling

Add proper catch2 support:
 - add catch2 as a submodule
 - add cmake function to add test easily
 - discover each test in test binary
 - remove copies of catch.hpp
 - do not try to process tests for rt1051

Do not test internals of utf8, only public interface (nasty bugs could
occur otherwise).

Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>

module-db/tests/ContactsTable_tests.cpp

@@ -1,8 +1,9 @@
-#include "../Databases/ContactsDB.hpp"
-#include "Tables/ContactsTable.hpp"
-#include "vfs.hpp"
+#include <catch2/catch.hpp>
 
-#include "catch.hpp"
+#include "Databases/ContactsDB.hpp"
+#include "Tables/ContactsTable.hpp"
+
+#include "vfs.hpp"
 
 TEST_CASE("Contacts Table tests")
 {