fix: make port transferables unique

[icidasset]

Fixes #3402

The transfer list, ie. the second argument to postMessage, should always contain unique values, multiple of the same pointers cause errors. This PR fixes that, see linked issue above for more info. My solution was to just make everything in the list unique by converting the array to a set and back. Let me know if this works, or if another solution is preferred.

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[achingbrain]

This looks great, thanks for submitting it. Please can you add a test to ensure regressions won't occur in future?

[icidasset]

@achingbrain I added a test for ipfs-message-port-server.
Can confirm that the test fails when I remove the code changes.

When the test is ran in the browser environment, it does complain about worker_threads not being available, even though I'm detecting the correct environment. Possibly webpack that tries to resolve the require before the code is actually being executed? 🤷 Anyhow, it does seem to actually run the tests.

[Gozala]

Thanks @icidasset for identifying this issue and also fixing it! It looks good. There would be few nice to haves, but I would much rather land this now and address them in followups. Feel free to take a stab if you like, otherwise I'll do it when I'll get around to it.

1. Implement solution does more or less following [...new Set(...transfer)] to eliminate duplicates. But ideally we would just make transfer itself into a Set so we don't have to eliminated duplicates.
2. postMessage actually accepts Sets (or any iterable) for transfer list, so conversion back to array is unnecessary.
3. I think it would probably be better to amend ipfs-message-port-protocol tests to exercise moving nodes e.g with duplicates CIDs.

[achingbrain]

I would much rather land this now and address them in followups.

@Gozala please can you open issues for the outstanding pieces of work so they don't get missed

[Gozala]

@Gozala please can you open issues for the outstanding pieces of work so they don't get missed

#3402 (comment)