[v1.12.0] New batch routes

[curquiza]

Related to meilisearch/integration-guides#307

Explanation of the feature

• New GET /batches & GET /batches/:uid routes
• New field in task object: batchUid

Usage: https://meilisearch.notion.site/Enhance-visibility-on-batched-tasks-1194b06b651f810b8fe0fab5d72846a8?pvs=74

TODO

👉 Check carefully the usage above to ensure your new methods and objects integrate all the functionnalities

• Create two new methods getBatch() and getBatches() triggering the appropriate new route (check out getTask and getTasks since the behavior will be pretty similar)
• A new batch object will probably be needed to be created.
• Ensure the task object can accept the batchUid field
• Add tests

⚠️ Make PRs pointing to bump-meilisearch-v1.12.0 and NOT main. Please do 1 PR for all of these changes, and not several.

[Strift]

Closed by #699