Introduce jvector-apis module and status tracker

[jshook]

[Updates 10/15]:

With some first-user input from Mark and some other cleanups and improved docs, the core code is tighter, safer, and cleaner. There were several files added in test, specifically to make it easy to understand the usage patterns for implementing tracked tasks.

I believe that we should have living examples where we can, and that means they should be tested. If necessary, we can put a group tag on the "example" tests to bypass them conveniently except for release-level tests. For now, they are enabled for review here.

[Previously ...]

The status tracking module may have use in both prod and test code, but we wanted to isolate and manage it better as a separate module. For modules like this, I propose we use a jvector-apis module. This is where you would put new modular functionality, like the status tracking API, which may be used by multiple modules. There is a good primer on this in the README in the module root.

For the status tracking API, this is a new facility to allow us to collect and share the status of internal jobs that are being run by jvector. The first use of it will be to ease testing and baseline work around performance and accuracy for different vector spaces and indexing configurations. However, it does have some hooks which may be lightweight enough to instrument prod code with, and this is a separate concern not addressed specifically in this PR. For now, this merely introduces the status tracking API, which will be pulled into the dataset streaming work once when ready.

There is a substantial amount of testing included in this PR. The demo scaffolding is there as a test layer for improving the API and making sure it is ergonomic and non-invasive enough to be added to extant code. If necessary, we can gate the unit tests of this module with an optional test group, but I'd like to see how it works as is first.

There are a couple of unrelated cleanups in this PR as well, from previous commits by other committers, around mvn exec configs, logger and test dependency inclusions which were not intended. I've personally contacted these committers and verified their intent before removing the extra deps and configurations.

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[MarkWolters]

Great documentation, that is appreciated. Commented a few minor concerns but overall looks very strong