Add ReduceBooleanRule (realm#2675)

* [reduce_boolean] Implement rule

* [reduce_boolean] Improve reason text

* [reduce_boolean] Fix new violations

* [reduce_boolean] Add CHANGELOG.md entry

* [reduce_boolean] Shorten rule name

* [reduce_boolean] Use regular map instead of compactMap

* [reduce_boolean] Match only possible syntax kinds

CHANGELOG.md

@@ -85,6 +85,7 @@
 #### Enhancements
 
 * Add `reduce_boolean` rule to prefer simpler constructs over `reduce(Boolean)`.  
+* Add `reduce_boolean` rule to prefer simpler constructs over `reduce(Boolean)`.
   [Xavier Lowmiller](https://github.com/xavierLowmiller)
   [#2675](https://github.com/realm/SwiftLint/issues/2675)