Extend entries from "AbstractSimpleObject" instead of "DataObject"

[zaietsv]

I'd like to suggest usage of "AbstractSimpleObject" instead of "DataObject" in following entries:

• Tevtex\CacheManagement\Model\Data\CachePurgeResponse
• Tevtex\CacheManagement\Model\Data\CacheToggleResponse

A class "Magento\Framework\DataObject" contains some extra properties not used in the current implementations. Since "CachePurgeResponse" and "CacheToggleResponse" are dedicated only for REST output, it could be advisable to extend them from a parent class "Magento\Framework\Api\AbstractSimpleObject". The "AbstractSimpleObject" has more lightweight structure comparing to the "DataObject".

Hopefully the approach will save a couple of miliseconds for the REST outputs.