Add Spinner manager

[filippobrizzi]

Description

The SpinnersManager allows to orchestrate the start and termination of multiple spinners.

The most important functionality is the waitAny function which allows to unblock as soon as one of the spinner terminates. In this way we can proceed to stop all of the other. This is very useful in the context of errors.

[lhruby]

Suggested change

	void waitAll();
	void waitAny();
	/// @brief blocks until all spinners are finished. If a single spinner throws an exception, it will not be propagated as the other spinners are still blocking.
	void waitAll();
	/// @brief wait until any spinner terminates or throws an exception, which allows for immediate exception handling.
	void waitAny();

The naming is clear, but given this is somewhat complex async behavior, I would add these two lines. I'm not sure waitAll is useful tbh, as it only is useful if the spinner terminates on its own AND does never throw, which seems a non-existing case. While it is elegant and adds completeness, I feel like removing it.