Refactor repo for consistency

[lucifercr07]

Fix below changes as part of playground-mono repo:

• Use the word DiceDB and not Dice, every where, there are variable and config places where the word Dice is used.
• Rename config “REQUEST_LIMIT” should be “REQUEST_LIMIT_PER_MIN”
• Rename config “REQUEST_WINDOW” should be “REQUEST_WINDOW_SEC”
• Remove package internals/cmds, we can move that struct to httpServer.go
• Rename the endpoint as /cli, let’s call it /shell/exec. (Remember to add Frontend changes for the same)
• All errors to be standardized w.r.t casing. We shall change everything to be lowercase.
• Change filename: server/httpServer.go -> server/http.go
• Update “errorResponse” function to JSON marshal and not string format.
• Currently log and slog are both being used, let’s just use slog everywhere.
• Rename pkg/util/helpers.go -> util/httpHelper.go

[rishavvajpayee]

Hey @lucifercr07 i can take this up

[lucifercr07]

@rishavvajpayee assigned, thanks for contributing.

[lucifercr07]

Closing, merged as part of #24