Add support for command HKEYS

[arpitbbhayani]

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

[ayushsatyam146]

Can I take this issue? @arpitbbhayani @JyotinderSingh

[swarajrb7]

@arpitbbhayani Can I pick this issue?

[lucifercr07]

@swarajrb7 assigned, thanks for contributing.

[RishabhC-137]

Can I work on this issue? @arpitbbhayani

[swarajrb7]

Have completed the working of the command. Currently working on writing integration_test.

[swarajrb7]

Update: Will create the PR in couple days.