Block Library: Add filter for inner blocks in the Navigation block

[afragen]

Description

Add filter to navigation.php to add ability to modify navigation block menu items.

Fixes #37717

Types of changes

New feature: filter menu items of navigation block.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).
• I've updated related schemas if appropriate.

[github-actions]

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[gziolo]

There is one filter that uses a different naming pattern. Let's align it with:

gutenberg/packages/block-library/src/navigation/index.php

Lines 333 to 345 in 8247dd0

	/**
	* Filters the fallback experience for the Navigation block.
	*
	* Returning a falsey value will opt out of the fallback and cause the block not to render.
	* To customise the blocks provided return an array of blocks - these should be valid
	* children of the `core/navigation` block.
	*
	* @since 5.9.0
	*
	* @param array[] default fallback blocks provided by the default block mechanic.
	*/
	return apply_filters( 'block_core_navigation_render_fallback', $fallback_blocks );

[gziolo]

@afragen, thank you for your contribution.