Few improvements

[MBkkt]

Purpose

Few fixes for coroutine:

• Add return_value(FutureBase<V, E>&& f), that allow to return value from future with same type as coroutine more free than co_return co_await f;
• Add return_value(StopTag) for cancel coroutine Future from function/Promise side
• Add ability to return error or result from coroutine Future
• Replace return_void with return_value(Unit) and co_return; with co_return {}; for allow use other return_value(...) in void coroutine

Fix BaseCore possible bug with incorrect static_cast ...

Few wait* fixes:

• Remove WaitGroup and AwaitGroup duplication
• Make WaitGroup and OneShotEvent better
• Make Wait single Future faster

Related Information

• Design document: ...
• Bench PR: ...

Testing

• This change is a trivial rework or code cleanup without any test coverage.
• This change is already covered by existing tests.
• This PR adds tests that were used to verify all changes.
• There are tests in an external testing repository: ...

[codecov]

Codecov Report

Merging #186 (d7ac8c2) into main (59a17ae) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #186   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           60        55    -5     
  Lines         1361      1303   -58     
=========================================
- Hits          1361      1303   -58     

Impacted Files	Coverage Δ
include/yaclib/algo/detail/when_all_impl.hpp	100.00% <ø> (ø)
include/yaclib/async/promise.hpp	100.00% <ø> (ø)
include/yaclib/coroutine/async_mutex.hpp	100.00% <ø> (ø)
include/yaclib/util/detail/mutex_event.hpp	100.00% <ø> (ø)
include/yaclib/algo/detail/wait_impl.hpp	100.00% <100.00%> (ø)
include/yaclib/algo/one_shot_event.hpp	100.00% <100.00%> (ø)
include/yaclib/algo/wait_group.hpp	100.00% <100.00%> (ø)
include/yaclib/async/detail/base_core.hpp	100.00% <100.00%> (ø)
include/yaclib/async/detail/core.hpp	100.00% <100.00%> (ø)
include/yaclib/async/detail/future_impl.hpp	100.00% <100.00%> (ø)
... and 14 more

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