Build updates

[JPercival]

…coverage

Description

• update to Java 21 for builds
• add Maven wrapper
• add code test coverage requirements of >=80% for new code
• prep for spotless integration

• Github Issue:
• [x] I've read the contribution guidelines
• [x] Code compiles without errors
• [x] Tests are created / updated
• [ ] Documentation is created / updated

By creating this PR you acknowledge that your contribution will be licensed under Apache 2.0

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