RFR: 8373101: JdkClient and JdkServer test classes ignore namedGroups field [v2]

[Matthew Donovan]

> This PR updates a couple test utility classes, JdkClient and JdkServer. Theseclasses extend AbstractPeer which contains a `namedGroup` field however, when creating/configuring the objects, the field is ignored. This PR just makes sure to include named groups if they are specified.

Matthew Donovan has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - refactored based on PR comments
 - Merge branch 'master' into abstractpeer
 - 8373101: JdkClient and JdkServer test classes ignore namedGroups field

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28664/files
  - new: https://git.openjdk.org/jdk/pull/28664/files/17d447f7..a26ab92d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28664&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28664&range=00-01

  Stats: 24712 lines in 480 files changed: 17252 ins; 5795 del; 1665 mod
  Patch: https://git.openjdk.org/jdk/pull/28664.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28664/head:pull/28664

PR: https://git.openjdk.org/jdk/pull/28664