Add test for DateTimeFormatterBuilder.appendGenericZoneText Bug: 296841248 Test: atest libcore.java.time.format.DateTimeFormatterBuilderTest (cherry picked from https://android-review.googlesource.com/q/commit:efbd64315017f866d347e08b0508511452606ed2) Merged-In: I6203a81707e0eb925c2d74932b431f3911874e42 Change-Id: I6203a81707e0eb925c2d74932b431f3911874e42