Move filesystem into Config

The filesystem object was available through ModuleContext.Fs(), but
gives too much access to the filesystem without enforicing correct
dependencies.  In order to support sandboxing the soong_build
process move the filesystem into the Config.  The next change will
make it private.

Bug: 146437378
Test: all Soong tests
Change-Id: I5d3ae9108f120fd335b21efd612aefa078378813
diff --git a/dexpreopt/dexpreopt_gen/dexpreopt_gen.go b/dexpreopt/dexpreopt_gen/dexpreopt_gen.go
index 009e906..6f51080 100644
--- a/dexpreopt/dexpreopt_gen/dexpreopt_gen.go
+++ b/dexpreopt/dexpreopt_gen/dexpreopt_gen.go
@@ -71,7 +71,7 @@
 		usage("path to module configuration file is required")
 	}
 
-	ctx := &pathContext{android.TestConfig(*outDir, nil)}
+	ctx := &pathContext{android.TestConfig(*outDir, nil, "", nil)}
 
 	globalConfig, _, err := dexpreopt.LoadGlobalConfig(ctx, *globalConfigPath)
 	if err != nil {