ESQL: Replace "representable" type error messages (elastic#131775)

Continuation of elastic#131694 (Issue: elastic#112006)

- Moved more messages from "representable" to "any type but counter types".
- Added missing docs on Count
- Added unsigned long and missing docs on Sample and Values
- Fixed Sample throwing error 500 on non-representable types

Author: ivancea

docs/changelog/131775.yaml

@@ -0,0 +1,5 @@
+pr: 131775
+summary: Replace "representable" type error messages
+area: ES|QL
+type: enhancement
+issues: []

docs/reference/query-languages/esql/_snippets/functions/types/count.md

@@ -22,6 +22,7 @@
 import static org.elasticsearch.xpack.esql.core.type.DataType.DATETIME;
 import static org.elasticsearch.xpack.esql.core.type.DataType.IP;
 import static org.elasticsearch.xpack.esql.core.type.DataType.NULL;
+import static org.elasticsearch.xpack.esql.core.type.DataType.isSpatial;
 
 public final class TypeResolutions {
 
@@ -71,6 +72,23 @@ public static TypeResolution isDate(Expression e, String operationName, ParamOrd
         return isType(e, dt -> dt == DATETIME, operationName, paramOrd, "datetime");
     }
 
+    /**
+     * @see DataType#isRepresentable(DataType)
+     */
+    public static TypeResolution isRepresentableExceptCounters(Expression e, String operationName, ParamOrdinal paramOrd) {
+        return isType(e, DataType::isRepresentable, operationName, paramOrd, "any type except counter types");
+    }
+
+    public static TypeResolution isRepresentableExceptCountersAndSpatial(Expression e, String operationName, ParamOrdinal paramOrd) {
+        return isType(
+            e,
+            (t) -> isSpatial(t) == false && DataType.isRepresentable(t),
+            operationName,
+            paramOrd,
+            "any type except counter and spatial types"
+        );
+    }
+
     public static TypeResolution isExact(Expression e, String message) {
         if (e instanceof FieldAttribute fa) {
             EsField.Exact exact = fa.getExactInfo();