A function tool call content block (type: "function_call").
type: "function_call"
@type t() :: %Gemini.Types.Interactions.FunctionCallContent{ arguments: map(), id: String.t(), name: String.t(), type: String.t() }
@spec from_api(map() | nil) :: t() | nil
@spec to_api(t() | map() | nil) :: map() | nil