Some changes to simplify the integration with Hibernate Reactive

[DavideD]

• Changes related to https://hibernate.atlassian.net/browse/HHH-20291
• Relax scope of some methods

Let me know if I need to create a JIRA

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license
and can be relicensed under the terms of the LGPL v2.1 license in the future at the maintainers' discretion.
For more information on licensing, please check here.

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Please make sure that the following tasks are completed:
Tasks specific to HHH-20291 (Task):

• Add test OR check there is no need for a test
• Update documentation as relevant: javadoc for changed API, documentation/src/main/asciidoc/userguide for all features, documentation/src/main/asciidoc/introduction for main features, links from existing documentation
• Add entries as relevant to migration-guide.adoc (breaking changes) and whats-new.adoc (new features/improvements)

[hibernate-github-bot]

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    ↳ Offending commits: [a850b85]
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By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license](https://www.apache.org/licenses/LICENSE-2.0.txt)
and can be relicensed under the terms of the [LGPL v2.1 license](https://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt) in the future at the maintainers' discretion.
For more information on licensing, please check [here](https://github.com/hibernate/hibernate-orm/blob/main/CONTRIBUTING.md#legal).

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[Copilot]

Pull request overview

This PR broadens a few internal extension points to simplify integration with Hibernate Reactive, mainly by relaxing visibility and allowing customization of StateManagement used by entity persisters.

Changes:

• Make selected internal classes/methods public/protected to enable reuse/override from Hibernate Reactive.
• Add new protected constructors to key *EntityPersister implementations that accept a Function<StateManagement, StateManagement> converter.
• Expose additional override points in mutation/collection coordinators (getBatchKey(), buildOperationGroup(), etc.).

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
hibernate-core/src/main/java/org/hibernate/persister/state/internal/AbstractStateManagement.java	Makes the base state-management implementation public to allow extension outside the package.
hibernate-core/src/main/java/org/hibernate/persister/entity/mutation/InsertCoordinatorStandard.java	Relaxes helper visibility (getPropertiesToInsert) for reuse in subclasses/extensions.
hibernate-core/src/main/java/org/hibernate/persister/entity/mutation/AbstractMutationCoordinator.java	Relaxes visibility of hasValueGenerationOnExecution for reuse by extensions.
hibernate-core/src/main/java/org/hibernate/persister/entity/UnionSubclassEntityPersister.java	Adds a protected constructor that forwards a StateManagement converter to the superclass.
hibernate-core/src/main/java/org/hibernate/persister/entity/SingleTableEntityPersister.java	Adds a protected constructor that forwards a StateManagement converter to the superclass.
hibernate-core/src/main/java/org/hibernate/persister/entity/JoinedSubclassEntityPersister.java	Adds a protected constructor that forwards a StateManagement converter to the superclass.
hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java	Introduces a new protected constructor with a StateManagement converter and applies it when assigning stateManagement.
hibernate-core/src/main/java/org/hibernate/persister/collection/mutation/RemoveCoordinatorStandard.java	Exposes getBatchKey() and buildOperationGroup() to support Reactive overrides and switches executor batch-key access to a method reference.

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[Copilot]

Typo in the comment: "teh" should be "the".

Suggested change

	// Used by Hibernate Reactive: it needs to override teh StateManagement
	// Used by Hibernate Reactive: it needs to override the StateManagement

[Copilot]

The parameter name statementManagerConverter is misleading here (it converts StateManagement, not statements) and is inconsistent with stateManagementConverter used in other persisters in this PR. Rename it (and its uses) to something like stateManagementConverter for clarity.

Suggested change

	final Function<StateManagement, StateManagement> statementManagerConverter)
	final Function<StateManagement, StateManagement> stateManagementConverter)

[Copilot]

statementManagerConverter.apply(...) can return null (or statementManagerConverter itself can be null when called from subclasses), which would leave stateManagement null and likely fail later with a harder-to-diagnose NPE. Consider validating the converter and its result (e.g., Objects.requireNonNull) and/or documenting that the converter must return a non-null StateManagement.

Suggested change

	stateManagement = statementManagerConverter.apply( persistentClass.getRootClass().getStateManagement() );
	stateManagement = Objects.requireNonNull(
	Objects.requireNonNull(
	statementManagerConverter,
	"statementManagerConverter must not be null"
	).apply( persistentClass.getRootClass().getStateManagement() ),
	"statementManagerConverter must not return null"
	);

[Copilot]

Inconsistent/misleading parameter name: statementManagerConverter converts StateManagement, and the other persister constructors in this PR use stateManagementConverter. Rename this parameter (and the corresponding super(...) argument) to match for readability and consistency.

Suggested change

	final Function<StateManagement, StateManagement> statementManagerConverter) throws HibernateException {
	super( persistentClass, cacheAccessStrategy, naturalIdRegionAccessStrategy, creationContext, statementManagerConverter );
	final Function<StateManagement, StateManagement> stateManagementConverter) throws HibernateException {
	super( persistentClass, cacheAccessStrategy, naturalIdRegionAccessStrategy, creationContext, stateManagementConverter );