Preserve LLMParams fields after Prompt.withUpdatedParams

[yakivy]

Motivation and Context

Preserves all LLMParams fields that were not updated during Prompt.withUpdatedParams, including subtype of LLMParams instance. The biggest impact of this change is on PromptExecutor.executeStructured, where it erases all the properties that were not updated by the method for Native structured completion requests.

Breaking Changes

No breaking changes.

Solution

I used .copy method from LLMParams that is properly overwritten by its children instead of LLMParamsUpdateContext.toParams

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Type of the changes

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tests improvement
• Refactoring

Checklist

• The pull request has a description of the proposed change
• I read the Contributing Guidelines before opening the pull request
• The pull request uses develop as the base branch
• Tests for the changes have been added
• All new and existing tests passed (checked jvmTest for prompt.* package, agent tests are red on my machine even before the PR)

[yakivy]

@Ololoshechkin @devcrocod could you take a look please?