Use custom mutex implementation instead of async-mutex

[simolus3]

To serialize some operations within a JavaScript context, we currently rely on the async-mutex package. That package is great, but we have some use-cases that are tricky to implement with it. In particular, it doesn't support timeouts (well, it does, but only globally on a mutex and we need per-acquire timeouts). Our workaround so far is to either ignore the timeout, or to acquire the mutex and then return it immediately if the timeout has expired. This is not a particularly good timeout implementation since we still need to wait for the mutex once even if the timeout has elapsed. It also doesn't support aborting an individual mutex request.

For the JS worker refactoring (#889) which introduces local mutexes where we've previously used navigator locks (with proper aborts), relying on async-mutex and ignoring timeouts would be a regression. So, considering that async-mutex doesn't do exactly what we need and since writing async mutexes in single-threaded languages is not that hard, this rolls our own mutex implementation. For the most part, it has the exact same API as async-mutex:

1. Calling and awaiting acquire() locks the mutex, and returns a function that unlocks it when invoked.
2. The runExclusive helper invokes a callback while them mutex is locked.

Because some of our mutex invocations rely on abort signals and others rely on timeouts, I've added an AbortSignal-based abort strategy to the implementation. In places where we've previously been using timeouts, the new timeoutSignal function is a wrapper around AbortSignal.timeout that should work in all places.

[changeset-bot]

🦋 Changeset detected

Latest commit: 465b193

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 10 packages

Name	Type
@powersync/react-native	Minor
@powersync/common	Minor
@powersync/web	Minor
@powersync/op-sqlite	Patch
@powersync/adapter-sql-js	Patch
@powersync/capacitor	Patch
@powersync/node	Patch
@powersync/nuxt	Patch
@powersync/tanstack-react-query	Patch
@powersync/diagnostics-app	Patch

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[stevensJourney]

I'm happy with these changes. Removing a dependency is always nice, removing it and replacing it with even more functionality is even better :)