IGNITE-6565: Use long type for size and keySize in cache metrics

[Александр Меньшиков]

I have done the task. Please review.

JIRA: https://issues.apache.org/jira/browse/IGNITE-6565
PR: https://github.com/apache/ignite/pull/3130
TC:
https://ci.ignite.apache.org/project.html?projectId=Ignite20Tests&branch_Ignite20Tests=pull%2F3130%2Fhead
UR: https://reviews.ignite.apache.org/ignite/review/IGNT-CR-416