8319161: GC: Make TestParallelGCThreads use createTestJavaProcessBuilder

[rsunderbabu]

Summary of change:

1. executeLimitedTestJava changed to executeTestJava to allow flags to be propagated to forked processes.
2. @requires vm.gc == null - this line is added to skip runs that use GC flags in test vm options. Allowing GC flags will result in VM initialization error ("Multiple garbage collectors selected").
3. Addition of ZGC to list of parallel collectors

Testing:
HS Tiers 1 and 2
Ran with all flag combinations in CI

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8319161: GC: Make TestParallelGCThreads use createTestJavaProcessBuilder (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/28566/head:pull/28566
$ git checkout pull/28566

Update a local copy of the PR:
$ git checkout pull/28566
$ git pull https://git.openjdk.org/jdk.git pull/28566/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 28566

View PR using the GUI difftool:
$ git pr show -t 28566

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/28566.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back rsunderbabu! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@rsunderbabu The following label will be automatically applied to this pull request:

• hotspot-gc

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 00: Full (74e72e0b)