Remove RAMUsageEstimator Unsafe calls [LUCENE-6239] #7301

This is unnecessary risk. We should remove this stuff, it is not needed here. We are a search engine, not a ram calculator.

Migrated from LUCENE-6239 by Robert Muir (@rmuir), resolved Feb 12 2015
Attachments: LUCENE-6239.patch (versions: 3)
Linked issues:

• compile with compact profiles [LUCENE-6069] #7131