[DISCO-4064] Resolve naming conflict and update suggest options

[misaniwere]

[DISCO-4064]

• Renamed SuggestApiError → MerinoSuggestApiError to avoid a naming conflict with the existing suggest component, which was breaking the Swift docs CI pipeline.
• For SuggestOptions, providers and client_variants now expect a list of strings as it's easier for the consumers. These values are joined as comma-separated values when sent to Merino.

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[tiftran]

lgtm, not sure if you want someone with more rust experience to give you the green light though 😅