[java] timely get rid of the SelectorManager threads

[joerg1985]

Description

In cases where a lot of WebDrivers are created, timely closed and there is no GC done, a lot of SelectorManager threads are running. Calling the GC explicit is not best practice, but it is the only way to stop these threads.

Has been reported in #11270

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

0.0% Coverage
0.0% Duplication

[pujagani]

The approach suggested here is not ideal since it manually calls GC. Closing in favor of #11345 which helps fix the same issue.