Convert coverageMutator to a TransitionMutator

Convert coverageMutator to a TransitionMutator as a step towards
variants-on-demand.

Bug: 319288033
Test: coverage_test.go
Test: treehugger coverage builds
Change-Id: Ic50c0040dea8b42c36b5d784221daa00b7b0d379
diff --git a/java/java.go b/java/java.go
index d18d915..d5d309f 100644
--- a/java/java.go
+++ b/java/java.go
@@ -1084,7 +1084,7 @@
 	return true
 }
 
-func (j *TestHost) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+func (j *TestHost) IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool {
 	return ctx.DeviceConfig().NativeCoverageEnabled()
 }