Convert tasks::task_manager::task::impl::release_resources() to a coroutine
to prepare for upcoming changes that will implement asynchronous resource
release.
This is a preparatory refactoring that enables future coroutine-based
implementation of resource cleanup logic.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
(cherry picked from commit 4c1f1baab4)
6b27459de3