Bad performance of rendering objects with many keys in tree mode

[josdejong]

In tree mode, an array with many items renders only the first 100 items and allow to "Show more". This makes sure the performane of rendering large arrays is fast. A similar case is an object with many keys. Right now, the editor renders all keys, which can be slow when having a lot of keys (like thousands).

In case of an object with many keys, it would be neat to only render the first 100 keys to keep performance good.