* Refactor some headers to use relative path from Mbed OS root.
* Refactor some data types to compile on 64bit machines.
* Refactor some debug traces to use mbed_trace.
Adding new modules inside the namespace could be breaking change for existing code base
hence add `using namespace::class` for classes newly added to mbed namespace to maintian
backwards compatibility.
MBED_NO_GLOBAL_USING_DIRECTIVE is added to remove auto-addition of namespace
Macro guard `MBED_NO_GLOBAL_USING_DIRECTIVE` is added around namespace, to avoid
polluting users namespace.