This commit addresses a series of issues identified by PHPStan, enhancing the overall type safety and robustness of the data structures.

- **BinaryHeap:** Corrected type inference by specifying the heap property as a `list`, which eliminates the need for explicit integer casting when removing elements.
- **TreeMap/TreeMapNode:** Fixed a potential null pointer exception in `balanceAfterInsertion` by adding a safety check for the grandparent node.
- **HashMap:** Refactored to use a consistent internal key handling mechanism, resolving type errors and adding proper support for object keys.
- **ArrayList:** Fixed a `Cannot cast mixed to string` error by explicitly handling the `resource` type.
- **phpstan.neon:** Cleaned up the configuration by removing obsolete ignored error patterns.