Add support for command JSON.STRLEN

[arpitbbhayani]

Add support for the JSON.STRLEN command in DiceDB similar to the JSON.STRLEN 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.

[apoorvyadav1111]

Hi @arpitbbhayani, Please assign this to me. I already have issue #412 assigned to me, but PR #439 is ready to be merged.

[arpitbbhayani]

@apoorvyadav1111 Assigned. Thank you for taking this up. Will merge your other PRs. Thanks for the patch.