#951 Design for Hash with expiry, Open for Review

[apoorvyadav1111]

Fixes: #951 Hi everyone,

I am looking for reviews on this PR and implementation of HASHMAP data with expiry support. This is the basic implementation of what Redis does (they have built it from scratch) which I think is something we can plan for the future. Currently, the design is similar to what we have for store but uses Go's built-in maps. I am looking for reviews concerning design, code quality, documentation, and optimizations. I will be creating benchmark tests + writing unit & integration tests for two new commands: HEXPIRE & HTTL.

Currently, we are migrating Hash-related commands and therefore, this PR either has to be merged before any of them is merged or I can wait for them to be merged and then rebase + refactor once again.

Post this merge, we can create issues for other expiry commands for Hashmap.

Thanks, Apoorv