Only store failed SignalSyncs

[chenBright]

What problem does this PR solve?

Issue Number:

Problem Summary:

_inuse_signal_syncs does not need to save successful SignalSyncs, only save failed SignalSyncs.

What is changed and the side effects?

Changed:

Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

• Please make sure your changes are compilable.
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[Copilot]

Pull Request Overview

This PR optimizes memory usage in the task tracer by only storing failed SignalSync objects instead of all SignalSync objects. Previously, successful SignalSyncs were temporarily added to _inuse_signal_syncs and then removed, which was unnecessary overhead.

• Removes the unconditional addition of SignalSync to _inuse_signal_syncs before the polling operation
• Adds SignalSync to _inuse_signal_syncs only when polling fails (EINTR errno case)
• Removes the pop operation for successful SignalSyncs since they're no longer added

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[wwbmmm]

LGTM