chore: Simpler Future<> without locking

[dranikpg]

Introduce simple future to replace boost code

replacing aligned_storage with optional, intrusive_ptr with shared_ptr and a mutex with event-count makes the code ten times smaller 🙂

[dranikpg]

Actually this is unsafe, need to fix this 😅

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.72%. Comparing base (d30de86) to head (c76ddb4). Report is 37 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #253 +/- ## ========================================== - Coverage 77.60% 76.72% -0.88% ========================================== Files 103 104 +1 Lines 7824 7791 -33 ========================================== - Hits 6072 5978 -94 - Misses 1752 1813 +61 ```

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