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.go b/finder/finder.go
index 2dd8e0b..ce17475 100644
--- a/finder/finder.go
+++ b/finder/finder.go
@@ -30,7 +30,7 @@
 	"sync/atomic"
 	"time"
 
-	"android/soong/fs"
+	"android/soong/finder/fs"
 )
 
 // This file provides a Finder struct that can quickly search for files satisfying