Fix mistakes after previous merge and make it compile.
Rewrite the function interpolating between time stamps as it was
written after the original pull request was created. Add unit tests
for it.
I couldn't help myself and also changed some enums to enum classes and
did some renames.
SystemTimeStamp used to be an opaque class, as it was provided by
`system_{linux/other/windows}.h`. Because of this, code dealt in
SystemTimeStamp pointers, and getting the current timestamp required a
memory allocation. Now SystemTimeStamp is just a
`std::chrono::time_point`, we can make the code cleaner and faster by
just directly keeping SystemTimeStamp instead of pointers around.
This commit actually fixes two problems causing the leak:
* DestroyTimeStamp not being called in CProfiler (my stupid mistake in 5fea22ff03)
* DestroyTimeStamp leaving null pointers in CSystemUtils::m_timeStamps (this was introduced by @piotrdz long ago when introducing smart pointers)
Tomasz Kapuściński