Choose between `select_field` and `select`; document and implement across app

cc @elias-ba , @stuartc - there are two different implementations for a select component in Form.

• choose the better one, delete the other
• add inline documentation to the better one (@doc)
• move all existing implementations of the losing function to use the new function

the functions below:

  def select_field(assigns) do
    select_classes = ~w[
      block
      w-full
      rounded-md
      border-secondary-300
      shadow-sm
      focus:border-primary-300
      focus:ring
      focus:ring-primary-200
      focus:ring-opacity-50
    ]

    opts =
      assigns_to_attributes(assigns, [:form, :name, :values]) ++
        [class: select_classes]

    ~H"""
    <%= select(@form, @name, @values, opts) %>
    """
  end

  def select(assigns) do
    select_classes = ~w[
      block
      w-full
      rounded-md
      border-secondary-300
      sm:text-sm
      shadow-sm
      focus:border-primary-300
      focus:ring
      focus:ring-primary-200
      focus:ring-opacity-50
    ]

    opts = assigns_to_attributes(assigns) ++ [class: select_classes]

    assigns = assigns |> assign(opts: opts)

    ~H"""
    <select {@opts}>
      <%= render_slot(@inner_block) %>
    </select>
    """
  end

Start in the Form component where select_field/1 and select/1 are defined, and search the application for usages of both functions. Compare their existing behavior, choose one, then verify that the losing function has no remaining callers and that the retained function has inline @doc documentation.