Add AI.INFO command

[lantiga]

We should write the equivalent of the Redis INFO command, to make it easy to write plugin for Prometheus, Telegraf, etc for monitoring (time to compute, number of requests, memory, state of cuda allocations, etc)

[lantiga]

Use Redis module INFO API

RedisModule_RegisterInfoFunc
RedisModule_InfoAddSection
RedisModule_InfoBeginDictField
RedisModule_InfoEndDictField
RedisModule_InfoAddFieldString
RedisModule_InfoAddFieldCString
RedisModule_InfoAddFieldDouble
RedisModule_InfoAddFieldLongLong
RedisModule_InfoAddFieldULongLong

[lantiga]

Decision is still implement AI.INFO and replicate the same info using the INFO API when Redis 6 is out.

[lantiga]

Addressing this in #259

[filipecosta90]

@lantiga closing this since it was already merged 👍