RFR: 8314610: hotspot can't compile with the latest of gtest because of <iomanip>

[Xin Liu]

This patch fixed a compilation error when we use the latest gtest. Because gtest has removed 
<iomanip> from its header files,  we should include it by ourself, or we can't find the 
definition of std::setw.

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

Commit messages:
 - 8314610: hotspot can't compile with the latest of gtest because of <iomanip>

Changes: https://git.openjdk.org/jdk/pull/15352/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15352&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314610
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15352.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15352/head:pull/15352

PR: https://git.openjdk.org/jdk/pull/15352