Use std::condition_variable_any with timed locking

[wezrule]

When #2267 was made we exclusively used std::condition_variable, this only accepts std::unique_lock which made it incompatible with our new nano::unique_lock. Unaware of alternatives a new condition_variable class was made which unfortunately depended on the boost context/fiber libraries.

However I recently discovered that there is a std::condition_variable_any class which is less constrained and accepts any BasicLockable type, which is compatible with our classes, so I am now using this which has removed the boost dependencies and some other code.

Also removed a CMake warning:

CMake Warning (dev) at CMakeLists.txt:35 (set):
implicitly converting 'NUMBER' to 'STRING' type.
This warning is for project developers.  Use -Wno-dev to suppress it.