In SpanNearQuery, add support for inOrder semantics equivalent to that of (Multi)PhraseQuery [LUCENE-8544]

As discussed in #9577, the semantics of phrase search differs among `(Multi)PhraseQuery`, `SpanNearQuery (inOrder=true)`, and `SpanNearQuery (inOrder=false)`:
- `(Multi)PhraseQuery`: incorporates the concept of order, and allows negative offsets in calculating slop/edit distance
- `SpanNearQuery (inOrder=true)`: incorporates the concept of order, and does _not_ allow negative offsets in calculating slop/edit distance
- `SpanNearQuery (inOrder=false)`: does not incorporate the concept of order at all

This issue concerns the possibility of adjusting `SpanNearQuery` to be configurable to support semantics equivalent to that of `(Multi)PhraseQuery`.

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Migrated from [LUCENE-8544](https://issues.apache.org/jira/browse/LUCENE-8544) by Michael Gibney (@magibney), updated Nov 05 2018

Start by reading the semantics described here and the linked discussion in #9577, then review the migrated LUCENE-8544 issue. Determine the agreed configurable behavior for SpanNearQuery and how it should match (Multi)PhraseQuery; done means the scope and equivalent in-order semantics are established and validated.

Written by the indexing model from the issue text.