Make EDSC builder test more robust to the order of evaluation

    EDSC builder test uses FileCheck to match the IR produced by EDSC in the
    textual order.  For mathematical operations, EDSC relies on overloaded
    operators.  Since they are essentially function calls, the order of evaluation
    of their operands is unspecified and differs between compilers.  Do not rely on
    a specific order of operands and just check they are all emitted before the
    last operation.  Give names to matched SSA values in order to make sure the
    right operands are used in relevant places.

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PiperOrigin-RevId: 249494995