RFR: JDK-8289509 : Improve test coverage for XPath Axes: descendant, descendant-or-self, following, following-sibling

[Mahendra Chhipa]

Added test cases for xpath Axis:
1. descendant
2. descendant-or-self
3. following
4. following-sibling

-------------

Commit messages:
 - JDK-8289509 : Improve test coverage for XPath Axes: descendant, descendant-or-self
 - JDK-8289509 : Improve test coverage for XPath Axes: descendant, descendant-or-self, following, following-sibling

Changes: https://git.openjdk.org/jdk/pull/10557/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10557&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289509
  Stats: 308 lines in 2 files changed: 308 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10557.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10557/head:pull/10557

PR: https://git.openjdk.org/jdk/pull/10557