RFR: 8255174: Vector API unit tests for missed public api code coverage

[Sandhya Viswanathan]

Additional tests to increase Vector API public method code coverage to > 99%.

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Commit messages:
 - 8255174: Vector API unit tests for missed public api code coverage

Changes: https://git.openjdk.java.net/jdk/pull/785/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=785&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255174
  Stats: 19359 lines in 67 files changed: 19259 ins; 5 del; 95 mod
  Patch: https://git.openjdk.java.net/jdk/pull/785.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/785/head:pull/785

PR: https://git.openjdk.java.net/jdk/pull/785