Add `ViewTrait::addToArrayParameter()` and more tests

[vjik]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌
Fixed issues	-

For example, this method will be useful for breadcrumbs:

// Add in view
$this->addToArrayParameter('breadcrumbs', $item1, $item2);

// Get in layout
$breadcrumbs = $this->getParameter('breadcrumbs') ?? [];

[samdark]

How about making parameters a collection instead?

// Add in view
$this->parameters()->add('breadcrumbs', $item1, $item2);

// Get in layout
$breadcrumbs = $this->parameters()->get('breadcrumbs') ?? [];

[samdark]

It will break BC though...

[samdark]

👍