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
1 file changed