[NEW] Add ENCODING subcommand aligned Redis

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/kvrocks/issues) and found no similar issues.

### Motivation

Adding support for the ENCODING subcommand.

As a first-timer, I was browsing through https://github.com/apache/kvrocks/issues/595 and https://kvrocks.apache.org/docs/supported-commands/#object-subcommands, I see that ENCODING (and 3 other OBJECT subcommands) is not yet supported.

From here, https://redis.io/docs/latest/commands/object-encoding/, I see that this subcommand was available from Redis 2.2.3. I am curious why kvrocks does not support it yet? If possible, could I open a PR to add support for it? @PragmaTwice

### Solution

I am not sure yet. I will do some research once this is issue is validated.

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!

Start with the supported-commands documentation and the Redis OBJECT ENCODING specification linked in the issue, then inspect Kvrocks' existing OBJECT subcommands. Done means ENCODING is supported with behavior aligned to Redis and validated by the project's command tests.

Written by the indexing model from the issue text.