[TOU] Make tool definitions required in validation

[ahibrahimm]

Description

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[Copilot]

Pull request overview

This pull request makes tool definitions a required input for the ToolOutputUtilizationEvaluator by setting optional_tool_definitions=False when initializing the ToolDefinitionsValidator. This aligns the evaluator's behavior with ToolInputAccuracyEvaluator, which already requires tool definitions.

Changes:

• Modified ToolDefinitionsValidator initialization to require tool_definitions parameter