Add support for generics

Search results are untyped (map[string]any) which makes this very unergonomic to use

Currently we're working around it with a custom search method

func searchCollection[TDoc any](ctx context.Context, collection string, params *api.SearchCollectionParams) (*Result[TDoc], error) {
	resp, err := typesenseApiClient.SearchCollection(ctx, collection, params)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode > 299 {
		return nil, utils.ErrHighStatusCode
	}
	var results Result[TDoc]
	err = json.NewDecoder(resp.Body).Decode(&results)
	if err != nil {
		return nil, err
	}
	return &results, nil
}

and matching types

type  Result[TDoc any] struct {
	GroupedHits []GroupedHit[TDoc] `json:"grouped_hits,omitempty"`
	Hits []*ResultHit[TDoc] `json:"hits,omitempty"`
...

Start at SearchCollection and the existing Result, GroupedHit, and ResultHit types; compare them with the custom generic implementation shown in the issue. Determine the supported generic search-result API and the affected response shapes. Done means callers can receive typed search results without maintaining a custom search method.