### Description

`stats x = count`  throws error `unknown column [count]` which is confusing since stats does not allow aliasing for existing columns but only points to aggregate functions.
Hence why the message should be `incorrect function declaration count, you forgot to add the parantheisis`. 
Same approach when dealing with a typo: `stats x = cont(*)` - `Unkown aggregate function cont - did you mean count()?`

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/VerifierTests.java
assertEquals(
            "1:25: argument of [avg(first_name)] must be [numeric], found value [first_name] type [keyword]",
            error("from test | stats count(avg(first_name)) by first_name")
        );
        assertEquals(
            "1:19: aggregate function's field must be an attribute or literal; found [length(first_name)] of type [Length]",
            error("from test | stats count(length(first_name)) by first_name")
        );
        assertEquals(
            "1:23: expected an aggregate function or group but got [emp_no + avg(emp_no)] of type [Add]",
            error("from test | stats x = emp_no + avg(emp_no) by emp_no")
        );
        assertEquals(
            "1:23: second argument of [percentile(languages, languages)] must be a constant, received [languages]",
            error("from test | stats x = percentile(languages, languages) by emp_no")
        );
        assertEquals(
            "1:23: second argument of [count_distinct(languages, languages)] must be a constant, received [languages]",
            error("from test | stats x = count_distinct(languages, languages) by emp_no")
        );
    }
    public void testDoubleRenamingField() {
        assertEquals(
            "1:44: Column [emp_no] renamed to [r1] and is no longer available [emp_no as r3]",
            error("from test | rename emp_no as r1, r1 as r2, emp_no as r3 | keep r3")
        );
    }
    public void testDuplicateRenaming() {
        assertEquals(
            "1:34: Column [emp_no] renamed to [r1] and is no longer available [emp_no as r1]",