Add `metadata` to the Object Store

[Jarema]

Add metadata to the Object Store bucket and object itself, as described in the design doc update: https://github.com/nats-io/nats-architecture-and-design/pull/224

Clients and Tools

• [ ] CLI @ripienaar
• [x] Go @piotrpio https://github.com/nats-io/nats.go/pull/1385
• [x] Java @scottf https://github.com/nats-io/nats.java/pull/1034
• [X] JavaScript @aricart https://github.com/nats-io/nats.deno/pull/544
• [x] .Net @scottf https://github.com/nats-io/nats.net/pull/840/
• [ ] C @levb
• [ ] Python @wallyqs
• [ ] Ruby @wallyqs
• [ ] Rust @Jarema @caspervonb

Other Tasks

• [ ] docs.nats.io updated @bruth
• [ ] Update ADR to Implemented
• [ ] Update client features spreadsheet

Client authors please update with your progress. If you open issues in your own repositories as a result of this request, please link them to this one by pasting the issue URL in a comment or main issue description.

[aricart]

@Jarema possibly need the same option for the KV bucket?