Running Asset Imports can lead to OutOfMemoryException (OOME) as every object's history is added to the cache

Issue Summary

This is reproducible on Data Center: (yes) 

This was introduced when fixing JSDSERVER-7225.

The change itself did not introduce this cache, but rather called a history service that was wired to this cache in imports for handling multiple import sources. This helped with fixing the problem of multi source imports, removing objects coming from other imports incorrectly.

There are two parts to this:

1. The cache isn't cleared at the end of the import
2. All those cache entries seem to be accessed only once. Meaning they have no value to be in the cache in the first place

Steps to Reproduce

1. Setup JSM 5.7 or later
2. Create object schema with lots of objects 
3. run several imports and create a history for the objects 

Expected Results

Import runs as expected.

Actual Results

Heap space is filling up with ehcache pertaining to Asset objects and object history. 

Workaround

Disable the following Feature Flag using the Dark Features settings page.

insight.import.update.missing.object.only.if.ever.imported

Please note, this will disable the fix for JSDSERVER-7225.