Added support for COMMAND command

[aashraybhandar1]

Summary
Added support for COMMAND command. Please review.
COMMAND is used to return an array with details about every DiceDB command.
redis documentation : https://redis.io/docs/latest/commands/command/

Changes

• Updated the existing evalCommand method to call the evalCommandDefault when no arguments are passed
• Implemented evalCommandDefault which returns an array with details about every DiceDB command
• made changes to resp.go to add appropriate formatting for []DiceCmdMeta and KeySpecs type
• Added test and Benchmark

Benchmark results

Issue: #144

[JyotinderSingh]

Please rebase the PR, we just had a large change go in which might've introduced conflicts.

[aashraybhandar1]

@JyotinderSingh due to this refatcoring, some changes of mine are breaking. The struct DiceCmdMeta is now not exposed to the package clientio which is needed to appropriately format the output for the COMMAND command. What should be the course of action? Will it be acceptable to move this struct to a new package called Models so that the cyclic dependency chain breaks?

[arpitbbhayani]

@aashraybhandar1 There are some test failures. Please fix the test failures and we will give it a final skim post that. thanks for the patch.

[aashraybhandar1]

@lucifercr07 thanks for the suggestion. I have tried implementing it with this new commit. Would appreciate your feedback on the same. Thank You!

[lucifercr07]

Thanks @aashraybhandar1 for PR, please check the review comment once.

[lucifercr07]

@aashraybhandar1 changes LGTM, will contain an issue to maintain the format parity with Redis.
Also we can update out command metadata to hold more info like flags and update arity for them.

[lucifercr07]

LGTM, Approved. Thanks @aashraybhandar1 for working on this.