TaskAdapter: Use std::shared_ptr<void> for c'tor / d'tor


Simplify internals a bit.

Change-Id: I8c7e835eefd3d3f2c3ca7c1bae07f503fbf342ba
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
commitdc2b3d1e4e4d963151963cf3149e677702bf24e7
parentda4aba009e87cdc09bcf49a87b2a87ef4ddc9f43
authorJarek Kobus <jaroslaw.kobus@qt.io>
committerMarc Mutz <marc.mutz@qt.io>
commit timeMon, 1 Jun 2026 19:09:56 +0000