Storage memory management

[benStre]

Closes https://github.com/unyt-org/datex-core-js-legacy/issues/53

This PR implements a garbage collection system for the DATEX pointer storage. This is a completely separate GC system from the runtime GC, and it is still a quite naive implementation, but it is essential for storage memory management.

The GC is not specific for a storage location, but works with all storage locations (Databases, local storage, indexed db) that implement the StorageLocation API. It works simultaneously across all storage locations.

Background: When we assume that all eternal pointers exist for "eternity", we don't need any kind of automatic storage management - pointers are added to the storage and updated, but never deleted. Before this PR, a developer could explicitly delete pointers from the storage, but they were not removed when they were no longer needed. This is a big problem for huge collections like maps and sets with lots of volatile, changing data (e.g. temporary log entries).

The basic idea for the new storage GC is to use a basic reference counting (RC) system.

• If a pointer is still directly or indirectly referenced by a storage item (which is essentially an eternal value binding), it is guaranteed to be kept in the storage.
• On the other hand, it can't be guaranteed that a pointer will be removed from storage once it is no longer accessible (e.g. when there is a circular reference). This is a fundamental problem of RC - in the future, we might switch to a different, more sophisticated GC algorithm (e.g. mark and sweep).

Addtional new features:

• Both StorageWeakMap and StorageWeakSets are now supported (with some limitations: https://github.com/unyt-org/datex-core-js-legacy/issues/57)
• Datex.Storage.printSnapshot() can be used for storage analyis and debugging

Initial storage allocations when running Datex.Storage.printSnapshot() in a new UIX base project:

[benStre]

@jonasstrehle this is a very essential part of the DATEX runtime - it would be great if you could also test it out with some eternal value examples in a UIX base project (Datex.Storage.printSnapshot() for verification) - and also make sure this change does not break any existing projects (the probability is very low)