Preserve empty interpolations (#5079)

* pass quote through grammar

* pass through initialChunk/finalChunk

* passing tests

* always unwrap string object

* fixes from code review

* preserve passthrough literals

* cleaner approach

* only wrap when data

* shift more string formatting into nodes

* RegexWithInterpolations wrap Call

* preserve heregexen

* fixes per code review

* fix merge

* fix from code review

* fixes from code review

* passing tests

* fixes from code review

* just define in nodes

* fix from code review

* add comment for toPrimitiveString()

* fix from code review

Author: helixbass