### Elasticsearch Version

8.1.0-SNAPSHOT (but also affects 7.x releases)

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

OSX

### Problem Description

While the docs state that `RANDOM(null) = null` that's not always the case.

### Steps to Reproduce

```
GET _sql?format=txt
{
  "query": """
  SELECT random(n), n FROM longs
  """
}
```

yields 

```
    random(n)     |       n       
------------------+---------------
0.7308781907032909|1              
0.7311469360199058|2              
0.3860252809814635|null           
```

Expected would be `null` for the last row.

### Logs (if relevant)

_No response_
x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/expression/function/scalar/math/MathFunctionProcessorTests.java
MathProcessor proc = new MathProcessor(MathOperation.FLOOR);
        assertNull(proc.process(null));
        assertNotNull(proc.process(randomLong()));
        assertEquals(3.0, proc.process(3.3));
        assertEquals(3.0, proc.process(3.9));
        assertEquals(-13.0, proc.process(-12.1));
    }
    public void testCeil() {
        MathProcessor proc = new MathProcessor(MathOperation.CEIL);
        assertNull(proc.process(null));
        assertNotNull(proc.process(randomLong()));
        assertEquals(4.0, proc.process(3.3));
        assertEquals(4.0, proc.process(3.9));
        assertEquals(-12.0, proc.process(-12.1));
    }
    public void testUnsignedLongAbs() {
        MathProcessor proc = new MathProcessor(MathOperation.ABS);
        BigInteger bi = randomBigInteger();
        assertEquals(bi, proc.process(bi));
    }
    public void testUnsignedLongSign() {
        MathProcessor proc = new MathProcessor(MathOperation.SIGN);
        for (BigInteger bi : Arrays.asList(BigInteger.valueOf(randomNonNegativeLong()), BigInteger.ZERO)) {
            Object val = proc.process(bi);
            assertEquals(bi.intValue() == 0 ? 0 : 1, val);
            assertTrue(val instanceof Integer);
        }
    }
}