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-utils/test/unittest_utils.cpp

@@ -6,7 +6,7 @@
 
 #define CATCH_CONFIG_MAIN // This tells Catch to provide a main() - only do this in one cpp file
 
-#include "catch.hpp"
+#include <catch2/catch.hpp>
 
 #include "Utils.hpp"
 
@@ -25,7 +25,7 @@ TEST_CASE("Split tests")
     REQUIRE(ret[5] == "FINISHED");
     REQUIRE(ret[6] == "");
 
-    ret       = utils::split(inputStr1, delimiter);
+    ret = utils::split(inputStr1, delimiter);
     REQUIRE(ret.size() == 3);
     REQUIRE(ret[0] == "OK");
     REQUIRE(ret[1] == "NO CARRIER");