Add support for nightly tests (#7538)

This PR adds the ability to download [nightly reference tests from the consensus-specs repo](https://github.com/ethereum/consensus-specs/actions/workflows/generate_vectors.yml). This will be used by spec maintainers to ensure that there are no unexpected test failures prior to new releases. Also, we will keep track of test compliance with [this website](https://jtraglia.github.io/nyx/); eventually this will be integrated into Hive.


  * A new script (`download_test_vectors.sh`) is added to handle downloads.
* The logic for downloading GitHub artifacts is a bit complex.
* Rename the variables which store test versions:
* `TESTS_TAG` to `CONSENSUS_SPECS_TEST_VERSION`.
* `BLS_TEST_TAG` to `BLS_TEST_VERSION`, for consistency.
* Delete tarballs after extracting them.
* I see no need to keep these; they just use extra disk.
* Consolidate `clean` rules into a single rule.
* Do `clean` prior to downloading/extracting tests.
* Remove `CURL` variable with GitHub token; don't need it for downloading releases.
* Do `mkdir -p` when creating directories.
* Probably more small stuff...

Makefile

@@ -218,6 +218,9 @@ run-state-transition-tests:
 # Downloads and runs the EF test vectors.
 test-ef: make-ef-tests run-ef-tests
 
+# Downloads and runs the nightly EF test vectors.
+test-ef-nightly: make-ef-tests-nightly run-ef-tests
+
 # Downloads and runs the EF test vectors with nextest.
 nextest-ef: make-ef-tests nextest-run-ef-tests
 
@@ -278,6 +281,10 @@ lint-full:
 make-ef-tests:
 	make -C $(EF_TESTS)
 
+# Download/extract the nightly EF test vectors.
+make-ef-tests-nightly:
+	CONSENSUS_SPECS_TEST_VERSION=nightly make -C $(EF_TESTS)
+
 # Verifies that crates compile with fuzzing features enabled
 arbitrary-fuzz:
 	cargo check -p state_processing --features arbitrary-fuzz,$(TEST_FEATURES)