[SUREFIRE-1941] Allow overriding PpidChecker OS command line in POM configuration

**[Marc Batchelor](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=mbatchelor)** opened **[SUREFIRE-1941](https://issues.apache.org/jira/browse/SUREFIRE-1941?redirect=false)** and commented

There are many Linux and Unix variants. The PpidChecker has received several fixes over time to handle various edge cases when checking to make sure that the process is still alive. When PpidChecker doesn't detect that the test is running because of some variant behavior as it relates to the output format of /bin/ps, the developer's only recourse is to disable forking which makes the test execution take longer.

This improvement would allow a configuration setting to override the default command issued to the operating system to provide the process status in the form that PpidChecker can use.

For example:

```

...

/other/bin/ps -o etime:1=,pid:1= -p %d

```

---

**Affects:** 2.22.2

**Issue Links:**
- [SUREFIRE-1940](https://issues.apache.org/jira/browse/SUREFIRE-1940) PpidChecker doesn't work with MacOS Docker Desktop

Start by locating PpidChecker and the plugin's POM configuration handling, then trace where the default operating-system command is assembled. The work is done when a ps-command setting can override that default and supply the format PpidChecker expects, while the existing default behavior remains intact.

Written by the indexing model from the issue text.