RFR: 8295229: Try to verify gtest version

Wed Oct 12 14:15:39 UTC 2022

Inspired by the comment https://github.com/openjdk/jdk/pull/10503#issuecomment-1275500585 for JDK-8294623, I realized we need to do at least some kind of version verification of gtest.

Since gtest do not properly declare its version, this can't be done exactly, but we can look at some tell-tales and rule out versions that are way too far off.

I also updated the testing documentation to point to the build information about how to point to the gtest source, and the version requirements.

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Commit messages:
 - 8295229: Try to verify gtest version

Changes: https://git.openjdk.org/jdk/pull/10677/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10677&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295229
  Stats: 26 lines in 3 files changed: 22 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/10677.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10677/head:pull/10677

PR: https://git.openjdk.org/jdk/pull/10677