[WIP] Update jfr-connection module to follow style guide

[Copilot]

Update jfr-connection module to follow style guide

Based on analysis of the jfr-connection module code against docs/style-guide.md, here are the minimal changes needed:

Analysis Summary

• Code formatting: Already passes spotlessCheck ✅
• Build and tests: All passing ✅
• Add final keyword to public non-internal classes where appropriate
• Add static imports for commonly used utility methods
• Ensure test classes follow package-protected visibility convention

Implementation Plan

• Make public non-internal classes final: JfrConnectionException, RecordingOptions, PredefinedConfiguration, JfcFileConfiguration, MapConfiguration, Recording
• Add static imports for: Objects.requireNonNull, Collections., Arrays.
• Remove public modifier from test classes to make them package-protected
• Run tests and spotlessApply to ensure all changes work properly

Fixes #258.

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