[SUREFIRE-2172] StringUtils: yet more of them

**[Elliotte Rusty Harold](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=elharo)** opened **[SUREFIRE-2172](https://issues.apache.org/jira/browse/SUREFIRE-2172?redirect=false)** and commented

This project contains not one, not two, but **three** different StringUtils classes that duplicate functionality in the JDK and elsewhere. One or two of them imght be built by shading other classes. They're even sometimes both imported in the same classes such as LegacyPojoStackTraceWriter:

import org.apache.maven.surefire.api.util.internal.StringUtils;

import static org.apache.maven.surefire.shared.utils.StringUtils.isNotEmpty;

Figure out what to do about this.

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**Remote Links:**
- [GitHub Pull Request #768
](https://github.com/apache/maven-surefire/pull/768)

Start by comparing the three StringUtils classes and their usages, including the conflicting imports in LegacyPojoStackTraceWriter. Review remote pull request #768 to understand work already attempted. Done would require a decided approach for the duplicate utilities and consistent updates across affected callers.

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