Move android/soong/fs to android/soong/finder/fs

The fs package is specific to finder, move it inside finder.

Bug: 70897635
Test: m checkbuild
Change-Id: Ie705f064a832141702a8e87fd59ed75c01018504
diff --git a/finder/finder_test.go b/finder/finder_test.go
index 1522c68..29711fc 100644
--- a/finder/finder_test.go
+++ b/finder/finder_test.go
@@ -21,12 +21,12 @@
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime/debug"
 	"sort"
 	"testing"
 	"time"
 
-	"android/soong/fs"
-	"runtime/debug"
+	"android/soong/finder/fs"
 )
 
 // some utils for tests to use