feat: extract interface HierarchicalTreeData from TreeData

[sclassen]

Description

TreeDataProvider currently takes a TreeData as its source. But it relies only on a few methods of TreeData.
This change extracts those methods into an interface. It then introduces a super class to TreeDataProvider which accepts a HierarchicalTreeData instead of a TreeData. A client has now the choice to either use the TreeData and the TreeDataProvider, or it can implement the HierarchicalTreeData interface and use the HierarchicalTreeDataProvider.

This change introduces a new interface and a new class but does not change or break any existing API.

Fixes #9808

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[CLAassistant]

All committers have signed the CLA.

[sclassen]

This is the minimal change I could find to satisfy the desire to have a custom tree data implementation as it is expressed in #9808.

• The extracted interface has only the minimal set of method required.
• All existing code is moved or untouched so no changes in behavior results.

The name of the new interface is semi optimal, as "hierarchical" is already used in other class names with a slightly different semantics.

[github-actions]

Test Results

 1 386 files  ±0   1 386 suites  ±0   1h 29m 50s ⏱️ +17s
 9 927 tests ±0   9 856 ✅ ±0  71 💤 ±0  0 ❌ ±0 
10 400 runs  ±0  10 320 ✅ ±0  80 💤 ±0  0 ❌ ±0 

Results for commit c23deb0. ± Comparison against base commit 6213adb.

♻️ This comment has been updated with latest results.

[sclassen]

I am not sure why this PR has the +1.0.0 tag.
No existing API or implementation is changed.
Only new interfaces/classes are added.

From my perspective this should qualify as a +0.1.0.

[mshabarov]

I am not sure why this PR has the +1.0.0 tag. No existing API or implementation is changed. Only new interfaces/classes are added.

From my perspective this should qualify as a +0.1.0.

It fell back to +1.0.0 because the check wasn't actually running until I restarted it. Now it shows +0.1.0.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud