[Meilisearch v1.53.0] Add `indexSize` and `usedIndexSize` to index stats

[Strift]

Context

Meilisearch v1.53.0 adds indexSize and usedIndexSize to per-index stats.

Objective

Update the SDK so index stats responses include the new indexSize and usedIndexSize fields returned by Get stats of index and per index in Get stats of all indexes.

• indexSize: size of the index DB (bytes by default; honour sizeFormat when supported)
• usedIndexSize: size of the used pages of the index DB (bytes by default; honour sizeFormat when supported)

Tasks

• Add indexSize and usedIndexSize to the index stats response shape
• Update test cases

[AubaidAhmedSaiyed]

Hey, I would like to work on this issue

[krishna3006b]

@Strift please review pr #990, i have fixed this