Add support for command `EXPIRETIME`

[arpitbbhayani]

Add support for the EXPIRETIME command in DiceDB similar to the EXPIRETIME 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.

[raknay]

@arpitbbhayani I would like to work on this Please assign it to me.

[arpitbbhayani]

@raknay Assigned the issue to you. Go for it.

It would be awesome if you keep posting updates to this issue so that we know you are working on it. If we see an inactivity of 7 days, we will remove your assignment. This is just to ensure that the project maintains its momentum and others are not blocked on this work.

But it really means a ton to us that you are contributing to this project. Thanks again.

[raknay]

@arpitbbhayani Was stuck with some personal work. Got free now. Will post the updates on the issue.