Fix ChaiScript#655: Async issues with threads outliving the chaiscrip…

…t engine (ChaiScript#656)

* Fix ChaiScript#655: Join async threads before engine destruction to prevent heap-use-after-free

Issues ChaiScript#632 and ChaiScript#636 (PRs ChaiScript#651 and ChaiScript#653) both stem from the same root cause: async
threads spawned via async() can outlive the Dispatch_Engine, accessing shared state
(global objects map, type maps) after it has been destroyed. The fix moves async()
registration from the stdlib module into ChaiScript_Basic, where spawned threads are
tracked via Dispatch_Engine. The engine's destructor now joins all outstanding async
threads before destroying shared data structures.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Address review: follow rule of 5, explicitly default move operations

Requested by @lefticus in PR ChaiScript#656 review.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: leftibot <leftibot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Fix lifetime of objects in ranged for loops

Currently this is going to incur a performance cost, but it's correct.

It may need to be reevaluated.

Closes ChaiScript#392

Merge branch 'develop' of github.com:ChaiScript/ChaiScript into develop

Update release notes

Update release notes for 5.8.5

Increment to 5.8.4

Add support for *& return types

Update to 5.8.2 release notes

Move debug over to windows build

Update release notes and prepare for 5.8.0