[MCHECKSTYLE-396] Add feature to generate Xpath suppressions as a goal

**[Linus Fernandes](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=fernal73)** opened **[MCHECKSTYLE-396](https://issues.apache.org/jira/browse/MCHECKSTYLE-396?redirect=false)** and commented

It would be nice to have an additional goal added to

the plugin to generate Xpath suppressions as currently possible through the CLI using the -g switch.

https://checkstyle.sourceforge.io/cmdline.html#Command_line_usage

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**Affects:** 3.1.1

**Issue Links:**
- [MCHECKSTYLE-382](https://issues.apache.org/jira/browse/MCHECKSTYLE-382) Add option to generate suppression xml file
(_**"duplicates"**_)

Start by comparing the requested Maven plugin goal with Checkstyle's CLI -g command and review the linked MCHECKSTYLE-382 duplicate for the current direction. Done means the plugin exposes a goal that generates XPath suppressions with behavior equivalent to the CLI option, with the expected output verified.

Written by the indexing model from the issue text.