Use std::optional if available.

Currently, SDK requires C++11 minimum.
So, boost::optional type is used for optional values.
For C++17 and above more convenient is to use std::optional instead.
This PR makes the optional type used configurable.

Fix Android build.

Relates-To: NLAM-23
Signed-off-by: sopov <[email protected]>

Author: asopov-here

olp-cpp-sdk-core/CMakeLists.txt

@@ -131,6 +131,7 @@ set(OLP_SDK_PORTING_HEADERS
     ./include/olp/core/porting/deprecated.h
     ./include/olp/core/porting/export.h
     ./include/olp/core/porting/make_unique.h
+        ./include/olp/core/porting/optional.hpp
     ./include/olp/core/porting/platform.h
     ./include/olp/core/porting/shared_mutex.h
     ./include/olp/core/porting/try_emplace.h