Add list_buckets function and tests to Object API

[jcreager]

This PR closes #168 and adds the ability to list Object bucket streams, replicating the nats CLI command nats object ls.

Credit to @lsxliron as this PR is based off of their PR to add the list_buckets function to the KV API.

[mmmries]

Hey @jcreager thank you so much for opening the issue and then putting up a PR ❤️ 💛 💙 💚 💜
On my first reading I don't see any problems here, but I'm short on time and haven't had much time to think about it. I'd like to take a second pass before making a final decision. Hopefully I can find time this week to review and leave any notes.

[jcreager]

Right on, thanks @mmmries.

[mmmries]

The only comment I left is something that would apply only for cases where Jetstream is hosting a large number of streams and we would potentially miss a bucket.

I think we can tackle that in a follow-up PR since it affects both of these functions and we'll probably want to handle them the same

[jcreager]

@mmmries I have created #172 to handle the pagination feature.

[jcreager]

Hey @mmmries just following up to see if you feel this is ok to merge.

[mmmries]

I'll get this released in a new patch version this evening. Thanks again for the contribution

[jcreager]

Thanks @mmmries! I'm happy I was able to make a contribution.

[mmmries]

Released as version 1.8.5 https://hex.pm/packages/gnat/1.8.5