This is the equivalent of the `field_masking_span` query, allowing users to
merge intervals from multiple fields - for example, to search for stemmed tokens
near unstemmed tokens.
* Add IntervalQueryBuilder with support for match and combine intervals
* Add relative intervals
* feedback
* YAML test - broekn
* yaml test; begin to add block source
* Add block; make disjunction its own source
* WIP
* Extract IntervalBuilder and add tests for it
* Fix eq/hashcode in Disjunction
* New yaml test
* checkstyle
* license headers
* test fix
* YAML format
* YAML formatting again
* yaml tests; javadoc
* Add OR test -> requires fix from LUCENE-8586
* Add docs
* Re-do API
* Clint's API
* Delete bash script
* doc fixes
* imports
* docs
* test fix
* feedback
* comma
* docs fixes
* Tidy up doc references to old rule