[Backport #2013 to 5.x] Add return type to GeneratorAwareInterface::setGenerator() and align related code

[github-actions]

Automated backport of #2013 to branch 5.x.

Do not modify this pull request.

Summary

Switch implied return type to explict static on GeneratorAwareInterface::setGenerator() and adjust all affected code accordingly.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Enhancement (improvement to existing functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactor (no functional changes)
• Chore (maintenance, dependencies, CI)

Related Issues

Test Plan

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code where necessary
• I have updated the documentation accordingly
• My changes generate no new warnings
• New and existing tests pass locally
• Any dependent changes have been merged and published