Move ImageMutator after archMutator

Move the ImageMutator to be registered just after the archMutator
in preparation for moving it between osMutator and archMutator.
Requries updating variants in a few tests that now run the
ImageMutator.

Bug: 142286466
Test: no change to build.ninja
Test: all soong tests
Change-Id: Ia9d2a7bc0e225bedec3c9a83ea04f471a931bf47
diff --git a/android/image.go b/android/image.go
index 5ec1b16..8424cf8 100644
--- a/android/image.go
+++ b/android/image.go
@@ -14,7 +14,7 @@
 
 package android
 
-// ImageInterface is implemented by modules that need to be split by the ImageMutator.
+// ImageInterface is implemented by modules that need to be split by the imageMutator.
 type ImageInterface interface {
 	// ImageMutatorBegin is called before any other method in the ImageInterface.
 	ImageMutatorBegin(ctx BaseModuleContext)
@@ -48,9 +48,9 @@
 	RecoveryVariation string = "recovery"
 )
 
-// ImageMutator creates variants for modules that implement the ImageInterface that
+// imageMutator creates variants for modules that implement the ImageInterface that
 // allow them to build differently for each partition (recovery, core, vendor, etc.).
-func ImageMutator(ctx BottomUpMutatorContext) {
+func imageMutator(ctx BottomUpMutatorContext) {
 	if ctx.Os() != Android {
 		return
 	}