Vine: Memory Leak Supplement

[JinZhou5042]

Proposed changes

This PR is a supplement of #3592.

The memory leak issue of FunctionCall tasks manifests on two sites:

• Python maintains references to task objects, failing to timely delete them.
• The manager's declared input and output buffers were not properly disposed of immediately after output retrieval.

While #3592 resolved the first issue, this PR remedies the second.

Comparison of consumed memory before and after changes in this PR with an example executed on 100 tasks:

Post-change actions

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Additional comments

This section is dedicated to changes that are ambitious or complex and require substantial discussions. Feel free to start the ball rolling.

[dthain]

This looks like the right approach.

While a user would normally call output on a successful task, there are some circumstances where they might not. (Maybe the task failed.)

Suggest that you set _input and _output_buffer to none when they are removed.

And then do a final check (and removal if needed) when the object is deleted.

[JinZhou5042]

Those are done.