Add support for command `HEXISTS`

[arpitbbhayani]

Add support for the HEXISTS command in DiceDB similar to the HEXISTS command in Redis. Please refer to the following commit in Redis to understand the implementation specifics - source.

Write unit and integration tests for the command referring to the tests written in the Redis codebase 7.2.5. For integration tests, you can refer to the tests folder. Note: they have used TCL for the test suite, and we need to port that to our way of writing integration tests using the relevant helper methods. Please refer to our tests directory.

For the command, benchmark the code and measure the time taken and memory allocs using benchmem and try to keep them to the bare minimum.

[HassanAarzoo]

Please assign this to me

[arpitbbhayani]

@HassanAarzoo Thanks for taking this up. assigned.

[HassanAarzoo]

I am starting to work on this. This is my first issue hence may take some time. @arpitbbhayani Is there a time limit associated with this?

[c-harish]

Hi @HassanAarzoo, are you still working on this? If not, I would like to take on this.

[HassanAarzoo]

@c-harish I am working on this. It will take me some time to complete it. Thanks for the message