RESP2->RESP3 result structure mapping

[slorello89]

Adding this as a follow on to redis/redis#12466 to keep track of our efforts to provide a mapping of the structural changes (e.g. ZRANGE moving from flat array -> array of tuples) between RESP2 and RESP3

This work has already been started by @chayim and @uglide see this doc

We should have 2 bits of output in redis.io from this:

1. A collated RESP2->RESP3 migration guide calling out these changes
2. The impacted command pages should be updated to reflect the correct result structures

CC: @mgravell, @NickCraver, @oranagra, @itamarhaber

[oranagra]

I've created another ticket to complement this one: #2512

[itamarhaber]

Yep yep yep!

@uglide will publish a draft shortly.

[uglide]

@itamarhaber @oranagra @slorello89 @mgravell Please review my PR with the converted migration guide #2513