Explicit Direct Include of C++ Standard Library Headers Are Required

[hassan-pdx]

ramses won't compile under Ubuntu 22.04 with its default GNU g++11 compiler due to the missing <cstddef> direct includes in the following files:

1. framework/PlatformAbstraction/include/PlatformAbstraction/Hash.h
2. client/ramses-client/ramses-text-api/include/ramses-text-api/TextLine.h
3. client/ramses-client/ramses-text-api/include/ramses-text-api/FontInstanceOffsets.h

Also, Abseil library is missing the <limits> header in: external/abseil/absl/synchronization/internal/graphcycles.cc