Fix /default parameters not displayed in Compare Runs

[rishabh998186]

This PR fixes an issue where default pipeline parameters are not shown in the Compare Runs view when a run is created from the UI without changing any parameter values. Previously, parameter values were only propagated when the user interacted with the inputs, so untouched defaults were missing from runtime_config and therefore from Compare Runs.

changes

NewRunParametersV2.tsx

Extend the existing parameter initialization effect to:

1. Build runtimeParametersInRealType from specParameters using convertInput for each parameter type.

2. Call handleParameterChange(runtimeParametersInRealType) once on mount/when spec changes so that:

 * Default parameter values are propagated to the parent (setRuntimeParameters).

 * These defaults are included in runtime_config even if the user does not modify any parameter fields.

3. Preserve the existing validation behavior with setIsValidInput.

NewRunParametersV2.test.tsx

1. Add a test: calls handleParameterChange with default values on mount:

Mount NewRunParametersV2 with a set of parameters of different types: STRING, NUMBER_INTEGER, BOOLEAN, LIST, and STRUCT, each with a defaultValue.

2.Assert that handleParameterChange is:

* Called exactly once.

*Called with the correctly converted runtime values.

3. Assert that these default values are rendered in the UI inputs.

Fixes: #12536

[google-oss-prow]

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[google-oss-prow]

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