tests: add test_wolfevent.c to CMakeLists.txt (cmake build lane)

api.c references test_wc_WolfEventDecisionCoverage via TEST_WOLFEVENT_DECLS,
but the new tests/api/test_wolfevent.c was only added to tests/api/include.am,
so the cmake unit-test build never compiled it -> undefined symbol at link
(GitHub Actions "WolfSSL CMake Build Tests" / Build wolfssl). Mirror the
include.am addition into the CMakeLists.txt unit_test source list.

CMakeLists.txt

@@ -4395,6 +4395,7 @@ if(WOLFSSL_EXAMPLES)
         tests/api/test_error.c
         tests/api/test_random.c
         tests/api/test_wolfentropy.c
+        tests/api/test_wolfevent.c
         tests/api/test_wolfmath.c
         tests/api/test_rsa.c
         tests/api/test_dsa.c