AssertingIndexSearcher should do basic QueryUtils/etc checks on every query [LUCENE-4934]

We can start with QueryUtils.check(query): which does some basic hashcode/equals checks.

Ideally we'd strengthen the checks as we fix problems: e.g. add explanations verifications (checkExplanations) and then finally the more intense check() that does more verifications with deleted docs/next/advance.

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Migrated from [LUCENE-4934](https://issues.apache.org/jira/browse/LUCENE-4934) by Robert Muir (@rmuir)
Attachments: [LUCENE-4934.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4934/LUCENE-4934.patch) (versions: 4)

Start by locating AssertingIndexSearcher and QueryUtils, then read how queries are executed and where QueryUtils.check(query) can be applied. Begin with the requested hashCode/equals checks on every query; completion should also reflect any explanation or deeper checks that the implementation scope adopts.

Written by the indexing model from the issue text.