Added support of module-based unit tests for `type_traits`.

* test/unit/jamfile: Added dependency on unit tests of `scope_guard`.
* test/unit/type_traits/jamfile: Removed `compile`, `compile-fail`, `run`
  and `run-fail` targets.
* test/unit/type_traits/identity_compile.cpp: Moved to
  `test/unit/type_traits/identity_run.cpp`.
* test/unit/type_traits/identity_run.cpp: Added test suites and test cases.
* test/unit/type_traits/is_callable_compile.cpp: Moved to
  `test/unit/type_traits/is_callable_run.cpp`.
* test/unit/type_traits/is_callable_run.cpp: Added test suites and test
  cases.
* test/unit/type_traits/is_decayed_compile.cpp: Moved to
  `test/unit/type_traits/is_decayed_run.cpp`.
* test/unit/type_traits/is_decayed_run.cpp: Added test suites and test
  cases.
* test/unit/type_traits/remove_rvalue_reference_compile.cpp: Moved to
  `test/unit/type_traits/remove_rvalue_reference_run.cpp`.
* test/unit/type_traits/remove_rvalue_reference_run.cpp: Added test suites
  and test cases.