Simple refactoring of prefix related functions.

Rename the two prefix-in-list funcs so that their usages are clearer.
Also find and replace all the code that essentially does either.

This introduces additional loops in some places, but I think the added
readability and simplicity outweighs the performance degradation, which
should be negligible anyway.

Test: m nothing
Test: TreeHugger
Change-Id: I37e2276ca0c815105ed0031f23c0b1264b480e4f
diff --git a/java/droiddoc.go b/java/droiddoc.go
index 959f1c7..6b39314 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -605,11 +605,8 @@
 				continue
 			}
 			packageName := strings.ReplaceAll(filepath.Dir(src.Rel()), "/", ".")
-			for _, pkg := range filterPackages {
-				if strings.HasPrefix(packageName, pkg) {
-					filtered = append(filtered, src)
-					break
-				}
+			if android.HasAnyPrefix(packageName, filterPackages) {
+				filtered = append(filtered, src)
 			}
 		}
 		return filtered