Reusable provider compatibility tests for jido_memory providers.

External provider packages can use this in their test suite:

defmodule MyProviderContractTest do
  use ExUnit.Case, async: true
  use Jido.Memory.Testing.ProviderContractCase

  def provider_under_test, do: Jido.Memory.Provider.MyProvider
  def provider_opts, do: [namespace: "agent:test"]
end