Merge #5371

5371: Composite embedders r=irevoire a=dureuill

# Pull Request

## Related issue
Fixes #5343 

## What does this PR do?
- Implement [public usage](https://www.notion.so/meilisearch/Composite-embedder-usage-14a4b06b651f81859dc3df21e8cd02a0)
- Refactor the way we check if a parameter is mandatory/allowed/disallowed for a given source
- Take the "nesting context" into account for computer if a parameter is mandatory/allowed/disallowed
- Add tests checking all parameters with all sources, and made sure the results didn't change compared with v1.13

## Dumpless Upgrade

- This adds a new value for an existing parameter => compatible without change
- This adds new optional parameters => compatible without change

Co-authored-by: Louis Dureuil <louis@meilisearch.com>

crates/meilisearch-types/src/error.rs

@@ -428,9 +428,10 @@ impl ErrorCode for milli::Error {
                     | UserError::InvalidUrl { .. }
                     | UserError::InvalidSettingsDocumentTemplateMaxBytes { .. }
                     | UserError::InvalidPrompt(_)
-                    | UserError::InvalidDisableBinaryQuantization { .. } => {
-                        Code::InvalidSettingsEmbedders
-                    }
+                    | UserError::InvalidDisableBinaryQuantization { .. }
+                    | UserError::InvalidSourceForNested { .. }
+                    | UserError::MissingSourceForNested { .. }
+                    | UserError::InvalidSettingsEmbedder { .. } => Code::InvalidSettingsEmbedders,
                     UserError::TooManyEmbedders(_) => Code::InvalidSettingsEmbedders,
                     UserError::InvalidPromptForEmbeddings(..) => Code::InvalidSettingsEmbedders,
                     UserError::NoPrimaryKeyCandidateFound => Code::IndexPrimaryKeyNoCandidateFound,