refactor(memory): centralize tracked runtime heap allocation

[TrixNEW]

Problem

The VM already has helpers such as allocArray(), but some code still directly allocates runtime objects and manually adds them to tracking collections.

For example:

const arr = try self.allocator.create(PhpArray);
try self.arrays.append(self.allocator, arr);

This can bypass pooling, duplicate ownership logic, and make allocation-failure cleanup inconsistent.

The same should be audited for arrays, objects, strings, reference cells, generators, fibers, etc.

Changes

Route runtime heap allocations through centralized helpers such as:

• allocArray()
• allocObject()
• allocOwnedString()
• allocPersistentString()
• allocRefCell()

Each helper should handle initialization, tracking, pooling, lifetime, and failure cleanup.

Acceptance criteria

• Runtime heap objects use centralized allocation paths.
• Pooling/tracking cannot be accidentally bypassed.
• Tracking allocation failures clean up correctly.
• No meaningful performance regression.