Add the possibility to pass view blocks to layouts

[giuscris]

This pull request adds a new method to the View class and improves the handling of template blocks when rendering layouts. The main focus is on enhancing template rendering flexibility and ensuring block definitions are properly managed during layout rendering.

Enhancements to template rendering:

• Added a defined(string $block): bool method to the View class, allowing templates to check if a specific block is defined during rendering. This method throws a RenderingException if called outside of the rendering context.

Improvements to layout rendering:

• Updated the output() method to copy the current view's blocks to the layout before rendering, ensuring that block definitions are available in the layout template.

[Copilot]

Pull request overview

Adds support for checking whether a template block exists during rendering and ensures blocks defined in a view are available to its layout, improving layout/template flexibility in Formwork’s view rendering system.

Changes:

• Added View::defined(string $block): bool to allow templates (including layouts) to conditionally render content based on whether a block was defined.
• Updated View::output() to propagate the current view’s $blocks into the layout before rendering it.

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[Copilot]

Assigning $this->layout->blocks = $this->blocks and then immediately writing $this->layout->blocks['content'] = ... forces PHP to separate/copy the whole $blocks array due to copy-on-write. If blocks can be large, consider adding the content entry before assigning blocks to the layout (or otherwise avoid writing to the layout blocks array right after the assignment) to prevent an unconditional array copy when rendering with a layout.