Deprecation `2025.05+`: content block `{"type": "text", "value": ...}` is deprecated

[Aaron1011]

The new content block formats are:

• {"type": "text", "text": "Some string"}
• {"type": "text", "arguments": {"key"": "value"}}

The text key will not be used as a template/JSON-schema input, while arguments will always be used as a template/JSON-schema input.

Using {"type": "text", "value": <json_value>} is deprecated - you should change it to:

• {"type": "text", "text": "my_text"} if you were previously passing a string for value
• {"type": "text", "arguments": {"key"": "value"}} if you were previously passing an object for value

[GabrielBianconi]

Let's remove the old behavior after we reach 2025.05+.

[shuyangli]

can we delete this now?