Make remaining mutable Queries immutable [LUCENE-7078]

See #7589
Mutable queries are an issue for automatic filter caching since modifying a query after it has been put into the cache will corrupt the cache. We should make all queries immutable (up to the boost) to avoid this issue.

Since they are part of the public API I would suggest splitting them in an immutable class and a builder like was done for most other Queries **before** releasing an official 6.x version

I did a quick scan through all derived classes of Query and I compiled the following list (ignoring sources in test or contrib folders)
Some of them are already marked as experimental (but should perhaps receive the "official" `@lucene`.experimental tag ?)
For some it's possibly not an issue since they should never end up in a filter cache (like MoreLikeThisQuery ?), but then a comment specifying the exception to the rule should perhaps be added.

- lucene/queries:
- org.apache.lucene.queries.CommonTermsQuery
- org.apache.lucene.queries.CustomScoreQuery (marked as `@lucene`.experimental)
- org.apache.lucene.queries.mlt.MoreLikeThisQuery
- lucene/suggest:
- org.apache.lucene.search.suggest.document.ContextQuery (marked as `@lucene`.experimental)
- lucene/facet:
- org.apache.lucene.facet.DrillDownQuery (marked as `@lucene`.experimental)

---
Migrated from [LUCENE-7078](https://issues.apache.org/jira/browse/LUCENE-7078) by Luc Vanlerberghe (@LucVL), updated Jun 08 2017
Linked issues:
- [SOLR-8802](https://issues.apache.org/jira/browse/SOLR-8802)
- #8120

Start by reviewing the listed query classes: CommonTermsQuery, CustomScoreQuery, MoreLikeThisQuery, ContextQuery, and DrillDownQuery, along with issue #7589 and linked issue #8120. Determine which remaining queries can be split into immutable classes and builders, then verify that mutability is limited to boost and document any query that should not enter the filter cache.

Written by the indexing model from the issue text.