Upgrade to Hibernate 6.2.8.Final

It looks like in the latest Hibernate there is some fix
in the persistent context where provided entity is updated
by the values from DB.

* Fix failing tests
* Migrate affected test classes to JUnit 5

**Cherry-pick to `6.1.x`**

# Conflicts:
#	build.gradle

Author: artembilan

build.gradle

@@ -67,7 +67,7 @@ ext {
     groovyVersion = '4.0.15'
     hamcrestVersion = '2.2'
     hazelcastVersion = '5.2.4'
-    hibernateVersion = '6.2.6.Final'
+    hibernateVersion = '6.2.8.Final'
     hsqldbVersion = '2.7.2'
     h2Version = '2.2.224'
     jacksonVersion = '2.15.2'