### Description

A query like `from employees | where true` is perfectly valid. So is `from employees | where still_hired`. In other words, a simple boolean expression is accepted, even if that expression is a field. For fields `where [field_name]` is the short version of `where [field_name] == true`.

But, for fields that are not booleans `from employees | where salary` for example, ESQL throws an exception:

```
                "type": "class_cast_exception",
                "reason": "class org.elasticsearch.compute.data.IntVectorBlock cannot be cast to class org.elasticsearch.compute.data.BooleanBlock (org.elasticsearch.compute.data.IntVectorBlock and org.elasticsearch.compute.data.BooleanBlock are in unnamed module of loader java.net.FactoryURLClassLoader @c6a692e)"
```

The error message should be more user-friendly, like validating the parameters of regular functions.
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/analysis/Verifier.java
private final Metrics metrics;
    public Verifier(Metrics metrics) {
        this.metrics = metrics;
    }
    /**
     * Verify that a {@link LogicalPlan} can be executed.
     *
     * @param plan The logical plan to be verified
     * @return a collection of verification failures; empty if and only if the plan is valid
     */
    Collection<Failure> verify(LogicalPlan plan) {
        Set<Failure> failures = new LinkedHashSet<>();
        
        plan.forEachUp(p -> {
            
            if (p.childrenResolved() == false) {
                return;
            }
            if (p instanceof Unresolvable u) {
                failures.add(fail(p, u.unresolvedMessage()));
            }
            
            else if (p.resolved()) {
                return;
            }