fix: gsoc lock

[nugaon]

This PR introduces a new locking mechanism with swarm.NewMultexLock which provides key based package level locking. The goal is to successfully run all test cases in the GSOC JS library with special attention to parallel requests.

Additionally, the StampItem changed to be based on identity address instead of chunk address so that GSOC chunks could be properly stamped.

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• [ ] I have added tests to cover my changes.
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Open API Spec Version Changes (if applicable)

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