OpenJDK 11: Merging in java.lang.String (lines() method)

This is part of merging upstream changes from OpenJDK 11.28. This CL
adds lines() method; and adds unit tests for it.

Bug: 202962059
Test: atest CtsLibcoreOjTestCases:test.java.lang.String.Lines
Change-Id: I6f71d8a0b97c302738f7aa4b58cce415eb5122dc
6 files changed