fix: support current upstream Java instrumentation list format

[zeitlinger]

Summary

• update the Java supported-library loader to handle the current upstream instrumentation-list.yaml list format
• keep compatibility with the older mapped representation used internally by otel-checker
• add test coverage for the new list-based YAML shape

Why

The check job was failing on both #267 and #279 because upstream open-telemetry/opentelemetry-java-instrumentation changed docs/instrumentation-list.yaml from a map shape to a list shape. otel-checker still assumed the old format and TestFindSupportedLibrary started failing.

Verification

• go test ./checks/sdk/java
• mise run check

[zeitlinger]

@jaydeluca here we still depend on the java format - not sure if that's still a good idea