Add Natjs KeyValue Store

[kobergj]

Adds a store nats-js-kv based on nats-js KeyValue interface. Instead of using streams to store the data (like the nats-js store does) it will store the data in jetstreams key value stores.

Some implementation details:

• optionally, keys can be base32 encoded to work around limited characters usable as keys for the store
• List calls can take quite long when there are many keys in a bucket. Might need a follow-up to fix
• I copied most tests from nats-js package to have the same test coverage. We should think about running the same testsuite against all stores.

I also needed to edit the .golangci.yml to make it possible getting green pipelines:

• The configuration for the depguard linter had a wrong format

[jochumdev]

While I like the base32 encoding here for simplicity, I believe this should be optional. Yeah, can be by default on.

Why:

• People might want theier keys human readable.
• When you know the limitations: https://docs.nats.io/nats-concepts/subjects#characters-allowed-for-subject-names you can be strict on that.
• Same K/V Store different users (python/rust/uvm.)

So what do you think?

[kobergj]

Yes. Good point. 👍 I introduced EncodeKeys option. Default is false because this is what I would expect.

[kobergj]

@jochumdev since this a new store and not just some fix or enhancement, I would very much appreciate your approve before I merge it