Add support for Redis SELECT command

[JyotinderSingh]

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

[JyotinderSingh]

While DiceDB currently doesn't support multiple logical databases, we need to support this command to unblock certain other tasks.

For now this can be implemented as a dummy command which just responds with RespOk.

[codeasashu]

@JyotinderSingh Can I work on this please?

[JyotinderSingh]

@JyotinderSingh Can I work on this please?

Assigned

[codeasashu]

@JyotinderSingh can you review PR?