swim: finish worker fiber on Tarantool shutdown

Let's make sure swim worker fiber is finished on Tarantool shutdown as
we are going to free fibers stacks. If fiber is not finished it's stack
may have references to objects on heap. Thus as fiber stack will be freed
we will have FP memory leaks under ASAN.

Let's make swim gc do not yield using asynchronuos deletion. This way we
will not use worker fiber for swim deletion. We are going to stop this
worker fiber before all swim object are collected.

Part of #9722

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