get_all_indexes should return a list of instance

[curquiza]

Currently, the get_all_indexes method in our SDKs returns a list of dict/struct/object, but not a list of Index instance. This is the only index-related method that does not return Index instance.

An instance is more convenient to manipulate than the object/struc/dict. See this example.

I suggest:

• we change the return of the current get_all_indexes: make it return a list of Index instances
• we provide a get_all_raw_indexes: a method that returns the list of dict/object/struct of indexes, so the response of the MeiliSearch server.

⚠️ No code duplication: use get_all_raw_indexes in get_all_indexes.

TODO

• meilisearch-dart
• meilisearch-dotnet
• meilisearch-go
• meilisearch-java
• meilisearch-js
• meilisearch-php
• meilisearch-python
• meilisearch-ruby
• meilisearch-rust
• meilisearch-swift (not applicable)