Implement inactivity scores ef tests unstable (#8807)

fixes issue #8750


  This PR enables the inactivity_scores reward EF tests from v1.7.0-alpha.2.

- Enabled Tests: Added the inactivity_scores handler to the rewards test suite.
- Fork Filtering: Updated the runner to execute these tests only on supported forks (Altair onwards), preventing directory-not-found errors on earlier forks.
- CI Coverage: Removed exclusions in the file access check script to ensures all new test vectors are fully tracked.


Co-Authored-By: romeoscript <romeobourne211@gmail.com>

Co-Authored-By: Eitan Seri-Levi <eserilev@gmail.com>

Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

testing/ef_tests/src/handler.rs

@@ -592,6 +592,15 @@ impl<E: EthSpec + TypeName> Handler for RewardsHandler<E> {
     fn handler_name(&self) -> String {
         self.handler_name.to_string()
     }
+
+    fn is_enabled_for_fork(&self, fork_name: ForkName) -> bool {
+        if self.handler_name == "inactivity_scores" {
+            // These tests were added in v1.7.0-alpha.2 and are available for Altair and later.
+            fork_name.altair_enabled()
+        } else {
+            true
+        }
+    }
 }
 
 #[derive(Educe)]