Message Title

This seems to be a regression introduced by https://hibernate.atlassian.net/browse/HHH-16281. When an entity is used on the root of a cacheable (sub)query, this entity gets serialized into the QueryKey. In our case this breaks hard because our entities do not implement Serializable, but I doubt it the cache entry would be any good if the entity were to implement Serializable. The attached testcase demonstrates the problem and fails with the following exception:

java.lang.ClassCastException: class org.hibernate.bugs.entities.MyEntity2 cannot be cast to class java.io.Serializable (org.hibernate.bugs.entities.MyEntity2 is in unnamed module of loader 'app'; java.io.Serializable is in module java.base of loader 'bootstrap')
	at org.hibernate.type.descriptor.java.ImmutableMutabilityPlan.disassemble(ImmutableMutabilityPlan.java:43)
	at org.hibernate.metamodel.mapping.BasicValuedMapping.addToCacheKey(BasicValuedMapping.java:71)
	at org.hibernate.metamodel.mapping.internal.BasicEntityIdentifierMappingImpl.addToCacheKey(BasicEntityIdentifierMappingImpl.java:388)
	at org.hibernate.query.internal.QueryParameterBindingsImpl.generateQueryKeyMemento(QueryParameterBindingsImpl.java:184)
	at org.hibernate.cache.spi.QueryKey.from(QueryKey.java:54)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.resolveJdbcValuesSource(JdbcSelectExecutorStandardImpl.java:422)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.doExecuteQuery(JdbcSelectExecutorStandardImpl.java:267)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.executeQuery(JdbcSelectExecutorStandardImpl.java:168)
	at org.hibernate.sql.exec.internal.JdbcSelectExecutorStandardImpl.list(JdbcSelectExecutorStandardImpl.java:93)
	at org.hibernate.sql.exec.spi.JdbcSelectExecutor.list(JdbcSelectExecutor.java:31)
	at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.lambda$new$0(ConcreteSqmSelectQueryPlan.java:109)
	at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.withCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:302)
	at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.performList(ConcreteSqmSelectQueryPlan.java:243)
	at org.hibernate.query.sqm.internal.QuerySqmImpl.doList(QuerySqmImpl.java:521)
	at org.hibernate.query.spi.AbstractSelectionQuery.list(AbstractSelectionQuery.java:367)
	at org.hibernate.query.sqm.internal.QuerySqmImpl.list(QuerySqmImpl.java:1084)
	at org.hibernate.query.Query.getResultList(Query.java:119)
	at org.hibernate.bugs.JPAUnitTestCase.hhh16025Test(JPAUnitTestCase.java:55)