Enable UnnecessarilyFullyQualified errorprone check

[trask]

Ported from opentelemetry-java. Combined both of these steps into this 1 PR

• Replace Xlint deprecation check with custom errorprone check opentelemetry-java#8061
• Enable errorprone's UnnecessarilyFullyQualified check opentelemetry-java#8078

[Copilot]

Pull request overview

This PR enables the UnnecessarilyFullyQualified ErrorProne check and introduces a custom ErrorProne check for deprecated API usage. The changes are ported from opentelemetry-java PRs #8061 and #8078, adapted for the contrib repository. The PR replaces javac's -Xlint:deprecation warning (which has issues with --release 8 due to JDK-8032211) with a custom ErrorProne check that properly honors @SuppressWarnings annotations.

Changes:

• Adds a new custom-checks module with the OtelDeprecatedApiUsage ErrorProne check
• Enables the UnnecessarilyFullyQualified ErrorProne check by removing its disable statement
• Removes unnecessary fully qualified type names across the codebase and adds proper imports

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 27 comments.

Show a summary per file

File	Description
settings.gradle.kts	Includes the new custom-checks module in the build
custom-checks/build.gradle.kts	Configures the custom-checks module with Java 21 source/target, compiler exports for javac internals, and circular dependency prevention
custom-checks/src/main/java/.../OtelDeprecatedApiUsage.java	Implements custom ErrorProne check for deprecated API usage with proper handling of same-class usage, import statements, and deprecated contexts
custom-checks/src/test/java/.../OtelDeprecatedApiUsageTest.java	Comprehensive test suite covering positive and negative cases for the custom check
custom-checks/src/main/resources/META-INF/services/.../BugChecker	Service loader registration for the custom check
buildSrc/.../otel.java-conventions.gradle.kts	Suppresses -Xlint:deprecation in favor of the custom ErrorProne check
buildSrc/.../otel.errorprone-conventions.gradle.kts	Removes disable statement for UnnecessarilyFullyQualified check, adds custom-checks dependency, and includes circular dependency prevention
dependencyManagement/build.gradle.kts	Adds error_prone_test_helpers dependency for testing
prometheus-client-bridge/.../MetricAdapter.java	Removes fully qualified Exemplar type and adds import
prometheus-client-bridge/.../MetricAdapterTest.java	Removes fully qualified List type and adds import
processors/.../InterceptableLogRecordExporterTest.java	Removes fully qualified Body type and adds import
opamp-client/.../OkHttpWebSocket.java	Removes fully qualified Request type and adds import
opamp-client/.../OkHttpSender.java	Removes fully qualified Request type and adds import
maven-extension/.../MavenDeployHandler.java	Removes fully qualified ArtifactRepository type and adds import
maven-extension/.../OtelExecutionListener.java	Removes fully qualified Context type and adds import
ibm-mq-metrics/.../JakartaPutGet.java	Removes fully qualified CMQC constant reference and uses import
gcp-auth-extension/.../GcpAuthExtensionEndToEndTest.java	Removes fully qualified SecureRandom type and adds import
disk-buffering/.../SpanDataImpl.java	Removes fully qualified InstrumentationLibraryInfo type and adds import
disk-buffering/.../LogRecordDataImpl.java	Removes fully qualified Body type and adds import
aws-resources/.../EcsResource.java	Removes fully qualified IncubatingAttributes constant reference and uses static import