.Net: Fix OllamaPromptExecutionSettings Clone() method to preserve Ollama-specific settings

[Copilot]

• Analyze the repository structure and understand the issue
• Review OpenAIPromptExecutionSettings implementation as reference
• Build and test the current Ollama connector
• Add Clone() method to OllamaPromptExecutionSettings
• Add Freeze() method to OllamaPromptExecutionSettings
• Change Stop property type from List to IList for consistency with OpenAI
• Add comprehensive tests for Clone() method
• Add test for Freeze() method
• Add ServiceId property to Clone() method (code review feedback)
• Add test to verify ServiceId is cloned correctly
• Build and test to verify all changes work correctly

Original prompt

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This section details on the original issue you should resolve

<issue_title>.Net: Bug: OllamaPromptExecutionSettings Clone() method does not clone Ollama specific settings</issue_title>
<issue_description>Describe the bug
Calling Clone() on OllamaPromptExecutionSettings instance returns PromptExecutionSettings with Temperature, TopK, TopP and MaxTokens settings lost

To Reproduce

var testSettings = new OllamaPromptExecutionSettings {  Temperature = (float)temperature, TopP = (float)topP };

// Throws `InvalidCastExeception` always as testSettings is of  `PromptExecutionSettings` type. 
// Additionally, testSettings do not contain temperature or topP parameter values (nothing in ExtensionData either)
var result = (OllamaPromptExecutionSettings) testSettings.Clone();

Expected behavior
Object is cloned correctly like in OpenAI provider

Platform

• Language: C#
• Source: 1.65.0
• AI model: Ollama qwen3:32b
• IDE: Visual Studio
• OS: Windows

Additional context

I think it should work like OpenAIPromptExecutionSettings, where all information is properly Cloned.
</issue_description>

<agent_instructions>Add the following methods to OllamaPromptExecutionSettings.cs

1. Clone
2. FromExecutionSettings

Use the implementations in OpenAIPromptExecutionSettings.cs as examples for how the methods should be implemented.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #13217

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