Enable HibernateHints.HINT_READ_ONLY hint to count() queries

This adds the HibernateHints.HINT_READ_ONLY to the `count()` calls.
Named queries can specify the hint in the @NamedQuery annotation, so
they don't need to be explicitly set.

- Fixes quarkusio#35978

extensions/panache/hibernate-orm-panache-common/runtime/src/main/java/io/quarkus/hibernate/orm/panache/common/runtime/AbstractJpaOperations.java

@@ -16,6 +16,7 @@
 import jakarta.transaction.TransactionManager;
 
 import org.hibernate.Session;
+import org.hibernate.jpa.HibernateHints;
 
 import io.agroal.api.AgroalDataSource;
 import io.quarkus.agroal.DataSource;
@@ -320,6 +321,7 @@ public Stream<?> streamAll(Class<?> entityClass, Sort sort) {
     public long count(Class<?> entityClass) {
         return (long) getEntityManager(entityClass)
                 .createQuery("SELECT COUNT(*) FROM " + PanacheJpaUtil.getEntityName(entityClass))
+                .setHint(HibernateHints.HINT_READ_ONLY, true)
                 .getSingleResult();
     }
 
@@ -333,7 +335,9 @@ public long count(Class<?> entityClass, String panacheQuery, Object... params) {
             return (long) bindParameters(
                     getEntityManager(entityClass)
                             .createQuery(PanacheJpaUtil.createCountQuery(entityClass, panacheQuery, paramCount(params))),
-                    params).getSingleResult();
+                    params)
+                    .setHint(HibernateHints.HINT_READ_ONLY, true)
+                    .getSingleResult();
         } catch (IllegalArgumentException x) {
             throw NamedQueryUtil.checkForNamedQueryMistake(x, panacheQuery);
         }
@@ -349,7 +353,9 @@ public long count(Class<?> entityClass, String panacheQuery, Map<String, Object>
             return (long) bindParameters(
                     getEntityManager(entityClass)
                             .createQuery(PanacheJpaUtil.createCountQuery(entityClass, panacheQuery, paramCount(params))),
-                    params).getSingleResult();
+                    params)
+                    .setHint(HibernateHints.HINT_READ_ONLY, true)
+                    .getSingleResult();
         } catch (IllegalArgumentException x) {
             throw NamedQueryUtil.checkForNamedQueryMistake(x, panacheQuery);
         }