Add pluggable overview/detail page sections for event definitions

[dennisoelkers]

Description

Introduces two new plugin extension points that let plugins render custom sections on the event definitions overview and detail pages:

• eventDefinitions.components.overviewPageSections — components rendered above the event definitions table on the overview page.
• eventDefinitions.components.detailPageSections — components rendered on the event definition detail page, each receiving the current eventDefinition as a prop.

Both entity types support an optional order field so registered sections render in a predictable sequence. Rendering is wired up via the new useEventDefinitionOverviewSections and useEventDefinitionDetailSections hooks in EventDefinitionsContainer and ViewEventDefinitionPage respectively.

/nocl WIP feature

Motivation and Context

Plugins need a way to augment the event definition overview and detail pages without modifying core components. These extension points provide the hooks for that.

How Has This Been Tested?

Added unit tests for both hooks (useEventDefinitionOverviewSections.test.tsx, useEventDefinitionDetailSections.test.tsx) covering the empty case and ordering behaviour.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have requested a documentation update.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.