Prevent dtor of generator in suspended fiber (#10462)

Generators that suspended a fiber should not be dtor because they will be
executed during the fiber dtor.

Fiber dtor throws

Prevent dtor of generator in suspended fiber (#10462)

Generators that suspended a fiber should not be dtor because they will be
executed during the fiber dtor.

Fiber dtor throws an exception in the fiber's context in order to unwind and
execute finally blocks, which will also properly dtor the generator.

Fixes GH-9916

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