Remove unused duplicate code and improve build configuration

[Copilot]

This PR removes unused code from the ApplicationInsights-Java repository, specifically addressing duplicate code that was marked with a TODO comment for removal.

Changes Made

1. Removed Duplicate Sampling Logic

• File: agent/agent-tooling/src/main/java/com/microsoft/applicationinsights/agent/internal/init/SecondEntryPoint.java
• Issue: Lines 178-182 contained duplicate sampling percentage logic that was also present in RuntimeConfigurator.updateSampling()
• Fix: Removed the duplicate code block and corresponding TODO comment

// REMOVED: Duplicate logic that was also in RuntimeConfigurator.updateSampling()
if (configuration.sampling.percentage != null) {
  BytecodeUtilImpl.samplingPercentage = configuration.sampling.percentage.floatValue();
} else {
  BytecodeUtilImpl.samplingPercentage = 100;
}

The RuntimeConfigurator.updateSampling() method is called later in the initialization flow and properly handles setting the sampling percentage, making this duplication unnecessary.

2. Improved Build Configuration

• File: .gitignore
• Added: /buildSrc/.kotlin/ to prevent Kotlin build artifacts from being committed
• Removed: Accidentally committed build error log file (buildSrc/.kotlin/errors/errors-1752940067370.log)

Validation

• ✅ All code compiles successfully
• ✅ Style checks (Spotless) pass
• ✅ Build process completes without errors
• ✅ Changes are minimal and surgical (only 7 lines changed total)
• ✅ No functionality impacted - the same sampling logic executes via RuntimeConfigurator.updateSampling()

Analysis

After comprehensive analysis of the codebase, this duplicate sampling percentage logic was the clear case of unused code that could be safely eliminated. Other potential candidates (like ETW test applications, @SuppressWarnings classes, etc.) represent legitimate architectural decisions rather than genuinely unused code.

Fixes #78.

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