Make aconfig flags generate a library instead of a srcjar.

Also add unit tests for the rest of device_config

Bug: 283475679
Test: m nothing (soong unit tests)
Change-Id: Iee18a1f2f2cbb23e8c8d84c54e903b32be29a693

java/java.go

@@ -273,6 +273,8 @@ type JavaInfo struct {
 	// JacocoReportClassesFile is the path to a jar containing uninstrumented classes that will be
 	// instrumented by jacoco.
 	JacocoReportClassesFile android.Path
+
+	// TODO: Add device config declarations here?
 }
 
 var JavaInfoProvider = blueprint.NewProvider(JavaInfo{})