etl/type_traits.h: Add support for type_identity (#905)
* etl/type_traits.h: Add support for type_identity
* test/test_type_traits.cpp: Add a test for etl::type_identity (type_identity_test_add(1.5f, 2) == 3.5f)
* Update test_type_traits.cpp
Use CHECK_CLOSE instead of CHECK for equality
