Convert some properties to Configurable properties

Focusing on the properties needed to remove soong config modules from
packages/modules/Virtualization.

- prebuilt_etc's src and srcs
- filegroup's srcs and exclude_srcs
- rust's cfgs

Bug: 342006386
Test: m nothing --no-skip-soong-tests
Change-Id: I6971da744a17955f98104948e6f9614776955782
diff --git a/android/filegroup.go b/android/filegroup.go
index a8326d4..ff0f74e 100644
--- a/android/filegroup.go
+++ b/android/filegroup.go
@@ -19,6 +19,7 @@
 	"strings"
 
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
 )
 
 func init() {
@@ -36,9 +37,9 @@
 
 type fileGroupProperties struct {
 	// srcs lists files that will be included in this filegroup
-	Srcs []string `android:"path"`
+	Srcs proptools.Configurable[[]string] `android:"path"`
 
-	Exclude_srcs []string `android:"path"`
+	Exclude_srcs proptools.Configurable[[]string] `android:"path"`
 
 	// The base path to the files.  May be used by other modules to determine which portion
 	// of the path to use.  For example, when a filegroup is used as data in a cc_test rule,
@@ -89,7 +90,7 @@
 }
 
 func (fg *fileGroup) GenerateAndroidBuildActions(ctx ModuleContext) {
-	fg.srcs = PathsForModuleSrcExcludes(ctx, fg.properties.Srcs, fg.properties.Exclude_srcs)
+	fg.srcs = PathsForModuleSrcExcludes(ctx, fg.properties.Srcs.GetOrDefault(ctx, nil), fg.properties.Exclude_srcs.GetOrDefault(ctx, nil))
 	if fg.properties.Path != nil {
 		fg.srcs = PathsWithModuleSrcSubDir(ctx, fg.srcs, String(fg.properties.Path))
 	}