Move the Once cache for dexpreopt.GlobalConfig into the dexpreopt
package.

Preparation for a future CL that will need to get the make-written
GlobalConfig from within dexpreopt.

Also rename the Load*Config functions to Parse*Config, since they don't
actually load the config files anymore.

Bug: 145934348
Test: m
Change-Id: I71df11c1e042ca8135d273a7263e9539ea3cd68f
diff --git a/java/java_test.go b/java/java_test.go
index b4795c0..f047486 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -99,7 +99,7 @@
 	t.Helper()
 
 	pathCtx := android.PathContextForTesting(config)
-	setDexpreoptTestGlobalConfig(config, dexpreopt.GlobalConfigForTests(pathCtx))
+	dexpreopt.SetTestGlobalConfig(config, dexpreopt.GlobalConfigForTests(pathCtx))
 
 	ctx.Register(config)
 	_, errs := ctx.ParseBlueprintsFiles("Android.bp")
@@ -118,7 +118,7 @@
 	ctx := testContext()
 
 	pathCtx := android.PathContextForTesting(config)
-	setDexpreoptTestGlobalConfig(config, dexpreopt.GlobalConfigForTests(pathCtx))
+	dexpreopt.SetTestGlobalConfig(config, dexpreopt.GlobalConfigForTests(pathCtx))
 
 	ctx.Register(config)
 	_, errs := ctx.ParseBlueprintsFiles("Android.bp")