[jdk11u-dev] RFR: 8289948: Improve test coverage for XPath functions: Node Set Functions

[Amos Shi]

Backport of [JDK-8289948](https://bugs.openjdk.org/browse/JDK-8289948)
- Clean Backport
- Test Compile error

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Commit messages:
 - Backport 57bf603b7332db86c39680d16b78f94a904daf46

Changes: https://git.openjdk.org/jdk11u-dev/pull/2361/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2361&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289948
  Stats: 354 lines in 4 files changed: 309 ins; 10 del; 35 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2361.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2361/head:pull/2361

PR: https://git.openjdk.org/jdk11u-dev/pull/2361