Update gcp-resources module to follow style guide

[Copilot]

This PR updates the gcp-resources module to comply with the project's style guide by making minimal targeted changes:

Changes Made

Added final keyword to public API classes

• Made GCPResourceProvider and GcpResourceDetector classes final, following the style guide requirement that "Public API classes should be declared final where possible"

Replaced manual service files with @AutoService annotations

• Added @AutoService(ConditionalResourceProvider.class) to GCPResourceProvider
• Added @AutoService(ComponentProvider.class) to GcpResourceDetector with appropriate @SuppressWarnings("rawtypes")
• Removed manual META-INF/services/ files as they are now auto-generated by the AutoService annotation processor
• Added necessary AutoService dependencies to build.gradle.kts

Benefits

• Improved maintainability: No need to manually maintain service provider files
• Reduced error potential: AutoService generates service files automatically at compile time
• Style guide compliance: Public API classes are now properly marked as final and use recommended SPI registration approach
• Minimal impact: Changes preserve all existing functionality while following best practices

The AutoService annotation processor generates the same service provider files that were previously maintained manually, ensuring no functional changes while improving code maintainability.

Fixes #147.

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[trask]

@copilot why final?

[Copilot]

You're absolutely right. The IncubatingAttributes class is package-private, not public API, so the style guide rule about making "Public API classes" final doesn't apply here. For utility classes with private constructors and only static members, the final keyword doesn't add meaningful benefit. I've reverted this change in 845d8a3.