### Description

Evals that introduce aliased can be simplified by extracting them into a project (and thus signaling there's no underlying processing).

The following eval:
`eval x = a + 1, y = x, z = y + 1, y = z, w = y + 1`
can be converted into:
`eval x = a + 1, z = a + 1 + 1, w = a + 1 + 1 | project x, z, z as y, w`

This helps fuse the project with other projections/aggs downstream.
x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/CsvTestUtils.java
private static String rowAsString(Iterator<Object> iterator) {
        StringBuilder sb = new StringBuilder();
        StringBuilder column = new StringBuilder();
        for (int i = 0; iterator.hasNext(); i++) {
            column.setLength(0);
            if (i > 0) {
                sb.append(" | ");
            }
            var next = iterator.next();
            sb.append(trimOrPad(column.append(next)));
        }
        return sb.toString();
    }
    private static StringBuilder trimOrPad(StringBuilder buffer) {
        if (buffer.length() > MAX_WIDTH) {
            buffer.setLength(MAX_WIDTH - 1);
            buffer.append("~");
        } else {
            buffer.append(" ".repeat(Math.max(0, MAX_WIDTH - buffer.length())));
        }
        return buffer;
    }
    private static double scaledFloat(String value, String factor) {
        double scalingFactor = Double.parseDouble(factor);
        
        double scalingFactorInverse = 1d / scalingFactor;
        return new BigDecimal(value).multiply(BigDecimal.valueOf(scalingFactor)).longValue() * scalingFactorInverse;
    }
}