Refactor implementation to unify tools usage for REST & realtime

[thekid]

See #15 (comment)

Works

$rest= new OpenAIEndpoint('https://'.getenv('OPENAI_API_KEY').'@api.openai.com/v1');

Console::writeLine($rest->api('/chat/completions')->invoke([
  'model'    => 'gpt-4o-mini',
  'tools'    => new Tools($functions),
  'messages' => [['role' => 'user', 'content' => $prompt]],
]));

Now also works

$rt= new RealtimeApi('wss://example.openai.azure.com/openai/realtime?'.
  '?api-version=2024-10-01-preview'.
  '&deployment=gpt-4o-realtime-preview'
);
$session= $rt->connect(['api-key' => getenv('AZUREAI_API_KEY')]);

Console::writeLine($rt->transmit([
  'type' => 'session.update',
  'session' => ['tools' => new Tools($functions)]
]));