Fix EZP-23459: eZContentObjectTreeNodeOperations::move missing features

Ensure that it checks whether view caching is enabled before clearing it.
Ensure that CacheThreshold is respected, if exceeded clear all cache.

https://jira.ez.no/browse/EZP-23459

(Part 3: Defer to script monitor will be moved to a separate issue)
1. Assign `eZINI::instance()` to a variable and use it below.
2. CS:

```php
if ( 
    eZINI::instance()->variable( 'ContentSettings', 'ViewCaching' ) === 'enabled' 
    && $childCount < (int)eZINI::instance()->variable( 'ContentSettings', 'CacheThreshold' )
)
{
    eZContentCacheManager::clearContentCacheIfNeeded( $objectID );
}
```