Remove `#ifdef UNITTEST` from MbedCRC.h

Production code should not contain any test-specific checks. Rather
than checking `UNITTEST`, MbedCRC.h can simply include in all cases
<mstd_type_traits> whose unit test stub exists.

Also remove the `UNITTEST` macro from CMake definitions of kvstore
unit tests which depend on MbedCRC.h.

drivers/include/drivers/MbedCRC.h

@@ -29,12 +29,7 @@
 #include "platform/SingletonPtr.h"
 #include "platform/PlatformMutex.h"
 
-#ifdef UNITTEST
-#include <type_traits>
-#define MSTD_CONSTEXPR_IF_HAS_IS_CONSTANT_EVALUATED
-#else
 #include <mstd_type_traits>
-#endif
 
 namespace mbed {
 /** \addtogroup drivers-public-api */

storage/kvstore/filesystemstore/tests/UNITTESTS/FileSystemStore/CMakeLists.txt

@@ -7,7 +7,6 @@ add_executable(${TEST_NAME})
 
 target_compile_definitions(${TEST_NAME} 
     PRIVATE
-        UNITTEST
         MBED_LFS_READ_SIZE=64
         MBED_LFS_PROG_SIZE=64
         MBED_LFS_BLOCK_SIZE=512

storage/kvstore/tdbstore/tests/UNITTESTS/TDBStore/CMakeLists.txt

@@ -5,11 +5,6 @@ set(TEST_NAME tdbstore-unittest)
 
 add_executable(${TEST_NAME})
 
-target_compile_definitions(${TEST_NAME} 
-    PRIVATE
-        UNITTEST
-)
-
 target_sources(${TEST_NAME}
     PRIVATE
         ${mbed-os_SOURCE_DIR}/storage/blockdevice/source/HeapBlockDevice.cpp