Add lint test property

Some libraries are only used for tests, but
are not test module types. These modules get warnings
about @VisibleForTesting usages when they really
shouldn't. Expose a test flag that module authors
can use to make lint treat a module as test code.

Bug: 235339747
Test: Manually tested applying it to SystemUI-tests
Change-Id: I1356749a669dc80a7725605d7159da27c9a211b4
diff --git a/java/app.go b/java/app.go
index 3c8fcd3..7a45855 100755
--- a/java/app.go
+++ b/java/app.go
@@ -1055,7 +1055,7 @@
 	module.appProperties.Use_embedded_native_libs = proptools.BoolPtr(true)
 	module.appProperties.AlwaysPackageNativeLibs = true
 	module.Module.dexpreopter.isTest = true
-	module.Module.linter.test = true
+	module.Module.linter.properties.Lint.Test = proptools.BoolPtr(true)
 
 	module.addHostAndDeviceProperties()
 	module.AddProperties(
@@ -1108,7 +1108,7 @@
 	module.appProperties.Use_embedded_native_libs = proptools.BoolPtr(true)
 	module.appProperties.AlwaysPackageNativeLibs = true
 	module.Module.dexpreopter.isTest = true
-	module.Module.linter.test = true
+	module.Module.linter.properties.Lint.Test = proptools.BoolPtr(true)
 
 	module.addHostAndDeviceProperties()
 	module.AddProperties(