Rename FixturePreparers to GroupFixturePreparers

FixturePreparers is a bad name for a method that creates a collection
of FixturePreparers for a couple of reasons:
* Conventionally it would be used as the name for []FixturePreparer if
  it is necessary to add behavior to that.
* There are many different types of collection, particularly when order
  matters.

Bug: 181070625
Test: m nothing
Change-Id: I55394ff369375dcac2d7b72e4d803a4818762d36
diff --git a/android/testing.go b/android/testing.go
index 5832796..691ebe1 100644
--- a/android/testing.go
+++ b/android/testing.go
@@ -48,7 +48,7 @@
 	return ctx
 }
 
-var PrepareForTestWithArchMutator = FixturePreparers(
+var PrepareForTestWithArchMutator = GroupFixturePreparers(
 	// Configure architecture targets in the fixture config.
 	FixtureModifyConfig(modifyTestConfigToSupportArchMutator),
 
@@ -73,7 +73,7 @@
 })
 
 // Prepares an integration test with build components from the android package.
-var PrepareForIntegrationTestWithAndroid = FixturePreparers(
+var PrepareForIntegrationTestWithAndroid = GroupFixturePreparers(
 	// Mutators. Must match order in mutator.go.
 	PrepareForTestWithArchMutator,
 	PrepareForTestWithDefaults,