Soong filesystem may install aconfig_flags.pb

By setting aconfig_flags: true, soong filesystem module installs the
aconfig_flags.pb file to its etc directory.

We need to define aconfigFilePaths to ModuleBase to store the list of
aconfig file paths that is generated from the GenerateBuildActions().
The aconfigFilePaths are collected when build the filesystem module
to build the aconfig_flags.pb for the filesystem image.

Bug: 335363964
Test: compare the cache list with those generated from make.
Change-Id: Ia32b566bf43174e94b9e610b9503608c6b583899

android/module.go

@@ -902,6 +902,9 @@ type ModuleBase struct {
 	installedInitRcPaths         InstallPaths
 	installedVintfFragmentsPaths InstallPaths
 
+	// Merged Aconfig files for all transitive deps.
+	aconfigFilePaths Paths
+
 	// set of dependency module:location mappings used to populate the license metadata for
 	// apex containers.
 	licenseInstallMap []string