remove guava usage from java code

[rbartl-pv]

Description

The PR removes the usage of the guava library from the java code.

Related Issue

Motivation and Context

Since the guava library bundle will not be available anymore in AEMaaCS and AEM6.5 LTS at some time the installation of the core bundle will fail without this removal.

How Has This Been Tested?

Screenshots (if appropriate):

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:

• [x] I have signed the Adobe Open Source CLA.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[rbartl-pv]

/cc @LSantha - as discussed here's a PR for the removal of guava